Số tiền còn lại sau khi đi chợ là:

900000-225000=675000(đồng)

Số tiền mua quần áo cho Long là: \(675000\times\frac35=405000\) (đồng)

Số tiền mẹ tiết kiệm được là:

675000-405000=270000(đồng)

a/ \(\left[\frac{4}{6}+\frac{14}{6}\right]+\left[\frac{7}{13}+\frac{19}{13}\right]+\left[\frac{17}{9}+\frac{1}{9}\right]=\frac{18}{6}+\frac{26}{13}+\frac{18}{9}=3+2+2=7\)

4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6

= (4/6 + 14/6) + (7/13 + 19/13) + (17/9 + 1/9)

= 18/6 + 26/13 + 18/9

= 3 + 2 + 2 

=7

1/9 + 7/12 + 2/9 + 1/12 + 4/12 + 6/9

= (1/9 + 2/9 + 6/9) + (7/12 + 1/12 + 4/12)

= 9/9 + 12/12

= 1 + 1

=2

\(\frac{9}{9}\times\frac{9}{8}\div\frac{7}{9}=1\times\frac{9}{8}\times\frac{9}{7}=\frac{9}{8}\times\frac{9}{7}=\frac{81}{56}\)

tick nha

\(\frac{9}{9}\)x\(\frac{9}{8}:\frac{7}{9}=\frac{9}{8}:\frac{7}{9}\) = \(\frac{9}{8}\) x\(\frac{9}{7}\) =\(\frac{81}{56}\)

a)\(\frac{2}{3}:\frac{4}{9}+\frac{1}{3}:\frac{4}{9}\)

=\(\frac{4}{9}:\left(\frac{2}{3}+\frac{1}{3}\right)\)

=\(\frac{4}{9}:1=\frac{4}{9}\)

b

a 9/4

b 49/40

c 36/35

d 144/441

\(\frac{2}{26}\)+\(\frac{9}{12}\)+\(\frac{4}{7}\)+\(\frac{9}{21}\)+\(\frac{12}{13}\)+\(\frac{20}{80}\) = \(\frac{1}{13}+\frac{3}{4}+\frac{4}{7}+\frac{3}{7}+\frac{12}{13}+\frac{1}{4}=\left(\frac{1}{13}+\frac{12}{13}\right)+\left(\frac{4}{7}+\frac{3}{7}\right)+\left(\frac{1}{4}+\frac{3}{4}\right)\)

= 1+ 1+ 1= 3

\(\frac{2}{26}+\frac{9}{12}+\frac{4}{7}+\frac{9}{21}+\frac{12}{13}+\frac{20}{80}\)

=\(\frac{1}{13}+\frac{3}{4}+\frac{4}{7}+\frac{3}{7}+\frac{12}{13}+\frac{1}{4}\)

=\(\left(\frac{1}{13}+\frac{12}{13}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{4}{7}+\frac{3}{7}\right)\)

= 1 + 1 + 1

= 3

like nha bạn!!!!

Câu 1:\(\frac{12}{23}\times\frac{9}{28}+\frac{11}{23}\times\frac{9}{28}\)

\(=\frac{9}{28}\times\left(\frac{12}{23}+\frac{11}{23}\right)\)

\(=\frac{9}{28}\times\frac{23}{23}\)

\(=\frac{9}{28}\times1\)

\(=\frac{9}{28}\)

Câu 2:

\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2\)

\(=\left(3+2+2+3\right)+\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)\)

\(=10+\frac{9}{9}\)

\(=10+1\)

\(=11\)

\(\frac{12}{23}x\frac{9}{28}+\frac{11}{23}x\frac{9}{28}=\)\(\left(\frac{12}{23}+\frac{11}{23}\right)x\frac{9}{28}\)\(=\) \(1x\frac{9}{28}=\frac{9}{28}\)

\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2\)\(=\) \(\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)+\left(3+2+3+2\right)\)\(=\) \(1+3+2+3+2=\)\(11\) 

\(a,\frac{3}{5}\times\frac{7}{9}=\frac{3\times7}{5\times9}=\frac{3\times7}{5\times3\times3}=\frac{7}{5\times3}=\frac{7}{15}\)

\(b,\frac{9}{13}\times\frac{17}{18}=\frac{9\times17}{13\times18}=\frac{9\times17}{13\times2\times9}=\frac{17}{13\times2}=\frac{17}{26}\)

Câu c,d tương tự

a. =7/15

b. = 17/26

c. = 52/33

d. =22/15

\(\frac{9}{22}\)và \(\frac{3}{11}\)

Ta có : \(\frac{3}{11}=\frac{6}{22}\)

\(\frac{9}{22}+\frac{6}{22}=\frac{15}{22}\)

Ủng hộ nhé ! 

quy đồng 3/11=6/22

6/22+9/22=15/22

đ/s:15/22

\(\frac{1}{2}+\frac{1}{2}=\frac{1+1}{2}=\frac{2}{2}=1\)

\(\frac{3}{4}+\frac{1}{4}=\frac{3+1}{4}=\frac{4}{4}=1\)

\(\frac{3}{9}+\frac{6}{9}=\frac{3+6}{9}=\frac{9}{9}=1\)

a, 1/2+1/2=1

b, 3/4+1/4=1

c, 3/9+6/9=1

k nha bn, ok