1

a) X=3/5 : 4/5

X=3/4

b) x=2/3 x 2/5

X=4/15

c) x=14/5 : 6/7

X=49/15

d) x=4/9 x 2/3

X= 8/27

2

7/15 < x < 4/3

7/15 < x < 20/15

X = 8/15;9/15;10/15;11/15;12/15;13/15;14/15;15/15;16/15;17/15;18/15;19/15

3

Hai năm nữa tuổi mẹ là

24:(4-1)x4 = 32 (tuổi)

Hai năm nữa tuổi con là

32:4=8 (tuổi)

Năm nay tuổi mẹ là

32-2=30 (tuổi)

Năm nay tuổi con là

8-2=6 (tuổi)

Đáp số tự ghi nhé

1a.\(\frac{3}{4}\)

 b.\(\frac{4}{15}\)

 c.\(\frac{49}{15}\)

 d.\(\frac{8}{27}\)

2. x = 1

3. Mẹ 30 tuổi, con 6 tuổi

câu 1 a=85

câu 2\(\frac{7}{18}\)

câu 3 \(\frac{1}{18}\)

Câu 1:a=85

Câu 2:x=7/18

Câu 3:x=1/18

a) \(\frac{3}{5}\times y+\frac{1}{2}:\frac{5}{3}-\frac{5}{4}=\frac{1}{2}\times\frac{1}{3}\)

\(\Rightarrow\frac{3}{5}\times y+\frac{3}{10}-\frac{5}{4}=\frac{1}{6}\)

\(\Rightarrow\frac{3}{5}\times y+\left(-\frac{19}{20}\right)=\frac{1}{6}\)

\(\Rightarrow\frac{3}{5}\times y=\frac{67}{60}\)

\(\Rightarrow y=\frac{67}{36}\)

b) \(\frac{4}{5}:y+\frac{1}{4}\times\frac{1}{6}-\frac{1}{2}=\frac{1}{3}\times\frac{5}{2}\)

\(\Rightarrow\frac{4}{5}:y+\frac{1}{24}-\frac{1}{2}=\frac{5}{6}\)

\(\Rightarrow\frac{4}{5}:y+\left(-\frac{11}{24}\right)=\frac{5}{6}\)

\(\Rightarrow\frac{4}{5}:y=\frac{5}{6}+\frac{11}{24}=\frac{31}{24}\)

\(\Rightarrow y=\frac{4}{5}:\frac{31}{24}=\frac{96}{155}\)

c) \(\frac{3}{5}\times y-\frac{4}{5}:3+\frac{1}{12}=\frac{3}{2}+\frac{1}{5}\)

\(\Rightarrow\frac{3}{5}\times y-\frac{4}{15}+\frac{1}{12}=\frac{17}{10}\)

\(\Rightarrow\frac{3}{5}\times y-\frac{4}{15}=\frac{97}{60}\)

\(\Rightarrow\frac{3}{5}\times y=\frac{113}{60}\)

\(\Rightarrow y=\frac{113}{36}\)

\(\frac{1}{2}:\frac{3}{2}:\frac{5}{4}:\frac{6}{5}:\frac{7}{6}:\frac{8}{7}\)

\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\)

\(=\frac{1\cdot\left(2\cdot5\cdot6\cdot7\right)}{8\cdot3\cdot\left(2\cdot5\cdot6\cdot7\right)}\)

\(=\frac{1}{24}\)

\(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\cdot\frac{8}{9}\cdot\frac{9}{10}\)

\(=\frac{1\cdot\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)}{\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)\cdot10}\)

\(=\frac{1}{10}\)

\(\left(2.8x-32\right):\frac{2}{3}=90\)

\(2.8\cdot x-32=90\cdot\frac{2}{3}\)

\(\frac{14}{5}x-32=60\)

\(\frac{14}{5}x=60+32\)

\(\frac{14}{5}x=92\)

\(x=\frac{230}{7}\)

B , c , d tương tự

\(\frac{3}{2}x+\frac{1}{5}x=\frac{5}{8}\)

\(Xx\left(\frac{3}{2}+\frac{1}{5}\right)=\frac{5}{8}\)

\(x=\frac{5}{8}:\left(\frac{3}{2}+\frac{1}{5}\right)\)

\(x=\frac{25}{68}\)

ta có X x ( \(\frac{3}{2}+\frac{1}{5}\)) = \(\frac{5}{8}\)

          X x \(\frac{17}{10}\) = \(\frac{5}{8}\)

           X = \(\frac{5}{8}:\frac{17}{10}\)

           X = \(\frac{25}{68}\)

\(\frac{2}{3}.\frac{4}{7}=\frac{8}{21}\)

\(\frac{3}{11}.2=\frac{6}{11}\)

\(4.\frac{2}{7}=\frac{8}{7}\)

\(\frac{8}{21}:\frac{2}{3}=\frac{8}{21}.\frac{3}{2}=\frac{21}{2.21}=\frac{1}{2}\)

\(\frac{3}{7}.\frac{7}{3}=\frac{21}{21}=1\)

\(\frac{3}{7}:\frac{3}{7}=\frac{3}{7}.\frac{7}{3}=\frac{21}{21}=1\)

lỡ tay bấm gửi trả lời luôn

\(\frac{2}{3}.\frac{1}{6}.\frac{9}{11}=\frac{2.9}{18.11}=\frac{2.9}{2.9.11}=\frac{1}{11}\)

\(\frac{2.3.4}{2.3.4.5}=\frac{6.4}{6.4.5}=\frac{24}{24.5}=\frac{1}{5}\)

\(\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times\left(1-\frac{1}{5}\right)\times\left(1-\frac{1}{6}\right)\times\left(1-\frac{1}{7}\right)\times\left(1-\frac{1}{8}\right)-\frac{1}{4}\times\frac{1}{2}\)

\(=\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}-\frac{1}{4}\times\frac{1}{2}\)

\(=\frac{2}{8}-\frac{1}{4}\times\frac{1}{2}\)

\(=\frac{2}{8}-\frac{1}{8}=\frac{1}{8}\)

d

\(a.\frac{4}{3}-\frac{3}{2}:X=\frac{1}{6}\)

           \(\frac{3}{2}:X=\frac{4}{3}-\frac{1}{6}\)

           \(\frac{3}{2}:X=\frac{8}{6}-\frac{1}{6}\)

           \(\frac{3}{2}:X=\frac{7}{6}\)

               \(X=\frac{3}{2}:\frac{7}{6}\)

              \(X=\frac{3}{2}\times\frac{6}{7}\)

              \(X=\frac{9}{7}\)

\(b.\left(X+\frac{2}{3}\right):\frac{1}{3}=\frac{41}{3}\)

    \(X-\frac{2}{3}=\frac{41}{3}.\frac{1}{3}\)

   \(X-\frac{2}{3}=\frac{41}{9}\)

  \(X=\frac{41}{9}+\frac{2}{3}\)

  \(X=\frac{41}{9}+\frac{6}{9}\)

 \(X=\frac{47}{9}\)

1) \(\frac{4}{5}.\frac{8}{3}.\frac{x}{7}=\frac{96}{105}\)

\(\frac{32.x}{105}=\frac{96}{105}\)

\(32x=96\)

\(x=3\)

Bài 1: Tìm \(x\)

\(\frac45\times\frac83\times\) \(\frac{x}{7}\) = \(\frac{96}{105}\)

\(\frac{32}{15}\) x \(\frac{x}{7}\) = \(\frac{32}{35}\)

\(\frac{x}{7}\) = \(\frac{32}{35}\) : \(\frac{32}{15}\)

\(\frac{x}{7}\) = \(\frac{32}{35}\) x \(\frac{15}{32}\)

\(\frac{x}{7}\) = \(\frac37\)

\(x=\frac37\times7\)

\(x=3\)

b; \(\frac74\times\frac{3}{x}\times\) \(\frac{11}{5}\) = \(\frac{231}{200}\)

\(\frac74\) x \(\frac{3}{x}\) = \(\frac{231}{200}\) : \(\frac{11}{5}\)

\(\frac74\times\frac{3}{x}\) = \(\frac{231}{200}\) x \(\frac{5}{11}\)

\(\frac74\) x \(\frac{3}{x}\) = \(\frac{21}{40}\)

\(\frac{3}{x}\) = \(\frac{21}{40}\) : \(\frac74\)

\(\frac{3}{x}\) = \(\frac{21}{40}\) x \(\frac47\)

\(\frac{3}{x}\) = \(\frac{3}{10}\)

\(x=3:\frac{3}{10}\)

\(x=3\times\frac{3}{10}\)

\(x=10\)