Tất cả dùng nhân chéo

a.3x=2.54=>x=36

b.15x=60=>x=4

c.2/3=4/6=>x=5

d.x=5;4(câu này ss từng phần)

Câu a:

\(x\) < \(\frac12\) + \(\frac13\) + \(\frac16\)

\(x\) < \(\frac36\) + \(\frac26\) + \(\frac16\)

\(x\) < \(\frac56\) + \(\frac16\)

\(x\) < \(\frac66\)

\(x\) < 1

Vì 0 < 1

Vì \(x\) là số tự nhiên nên \(x\) = 0

Câu b:

0 < \(x\) < \(\frac12\) + \(\frac23\) + \(\frac34\)

0 < \(x\) < \(\frac{6}{12}\) + \(\frac{8}{12}\) + \(\frac{9}{12}\)

0 < \(x\) < \(\frac{14}{12}\) + \(\frac{9}{12}\)

0 < \(x\) < \(\frac{23}{12}\)

0 < \(x\) < 1\(\frac{11}{12}\)

Vì 0 < 1 < 1\(\frac{11}{12}\)

Mà \(x\) là số tự nhiên nên \(x\) = 1

\(a,\frac{2}{3}=\frac{x}{54}\)

\(\Rightarrow2.54=3x\)

\(\Rightarrow3x=108\)

\(\Rightarrow x=108:3=36\)

\(b,\frac{10}{x}=\frac{15}{6}\)

\(\Rightarrow10.6=15x\)

\(\Rightarrow15x=60\)

\(\Rightarrow x=60:15=4\)

\(c,\frac{2}{3}< \frac{x}{6}< 1\)

\(\Rightarrow\frac{4}{6}< \frac{x}{6}< \frac{6}{6}\)

\(\Rightarrow4< x< 6\)

\(\Rightarrow x=5\)

\(d,1< \frac{6}{x}< 2\)

\(\Rightarrow\frac{6}{6}< \frac{6}{x}< \frac{6}{3}\)

\(\Rightarrow6< x< 3\)

\(\Rightarrow x=5;4\)

a)x=54.2:3=36

b)x=10.6:15=4

c)x = 5

d)x=4 hoặc x=5

a) 2/3=36/54  => x=36

b)15/6=10/3  =>x=3

\(a,\frac{2}{3}=\frac{x}{54}\Rightarrow x=\frac{2\times54}{3}\Rightarrow x=36\)

\(b,\frac{10}{x}=\frac{15}{6}\Rightarrow x=\frac{10\times6}{15}\Rightarrow x=4\)

\(c,\frac{2}{3}< \frac{x}{6}< 1\Rightarrow\frac{2}{3}\times6< x< 1\times6\Rightarrow4< x< 6\)

\(\frac{2}{7}< \frac{4}{x}< \frac{1}{3}\)

\(\Rightarrow\frac{4}{14}< \frac{4}{x}< \frac{4}{12}\)

\(\Rightarrow\frac{4}{14}< \frac{4}{13}< \frac{4}{12}\)

Vậy x = 13

1. ^{\(\frac{2}{7}< \frac{4}{x}< \frac{1}{3}=\frac{4}{14}< \frac{4}{x}< \frac{4}{12}\)}

\(x=0\)

Câu a:

\(x\) < \(\frac12\) + \(\frac13\) + \(\frac16\)

\(x\) < \(\frac36+\frac26+\frac16\)

\(x\) < \(\frac56\) + \(\frac16\)

\(x\) < 1

Vì 0 < 1

Mà \(x\) là số tự nhiên nên \(x\) = 0