Question

What percentage of muscle weight would you have if 60 pounds out of 140 pounds is muscle weight? If muscle weight is 90 pounds, how much does the person weigh?

Answer 1

$\bf \begin{array}{ccllll} total\ weight&muscle\ weight\\ -----&-----\\ 140&60\\ x&90 \end{array}\implies \cfrac{140}{x}=\cfrac{60}{90}$

solve for "x".