Question

a, 7/x = 3/12                                  b, X +X x 1/4 : 2/7 + X : 2/9 = 255

Answer 1

a) 7/x = 3/12= 1/4

x = 28

b) \(x+x\cdot\frac{1}{4}:\frac{2}{7}+x:\frac{2}{9}=255\)

\(x+x\cdot\frac{7}{8}+x\cdot\frac{9}{2}=255\)

\(x.\left(1+\frac{7}{8}+\frac{9}{2}\right)=255\)

\(x\cdot\frac{51}{8}=255\Rightarrow x=40\)

Answer 2

a) \(\frac{7}{x}=\frac{3}{12}=>7.12=3.x=>x=\frac{7.12}{3}=28\)28

Answer 3

a) =28 thôi

Answer 4

a) 7/x = 3/12 

<=> x . 3 = 7 . 12 

<=> x . 3 = 84 

<=> x = 84 : 3 

<=> x = 28 

Vậy x = 28 

Answer 5

\(a,\text{ }\frac{7}{x}=\frac{3}{12}=\frac{1}{4}=\frac{7}{28}\)

\(\Rightarrow\text{ }x=28\)

\(b,\text{ }x+x\text{ x }\frac{1}{4}\text{ : }\frac{2}{7}+x\text{ : }\frac{2}{9}=255\)

     \(x+x\text{ x }\frac{7}{8}+x\text{ x }\frac{9}{2}=255\)

     \(x\text{ x }\left(1+\frac{7}{8}+\frac{9}{2}\right)=255\)

     \(x\text{ x }\frac{51}{8}=255\)

     \(x=255\text{ : }\frac{51}{8}\)

\(x=40\)