Question

A boy painted 3/4 of a wallusing 1/7 of a can of paint. How many walls can he paint using 1 can of paint?

Answer 1

`\bf \begin{array}{ccll} wall&paint\\ \cline{1-2}\\ (3)/(4)&(1)/(7)\\\\ x&1 \end{array}\implies \cfrac{~~(3)/(4)~~}{x}=\cfrac{~~(1)/(7)~~}{1}\implies \cfrac{~~(3)/(4)~~}{(x)/(1)}=\cfrac{1}{7}\implies \cfrac{3}{4}\cdot \cfrac{1}{x}=\cfrac{1}{7} \\\\\\ \cfrac{3}{4x}=\cfrac{1}{7}\implies 21=4x\implies \cfrac{21}{4}=x\implies 5(1)/(4)=x`