Question

cum se afla x din proportia
36-x 
_____=_7     
 28+x   9

Answer 1

$\displaystyle \frac{36-x}{28+x} = \frac{7}{9} \Rightarrow 9(36-x)=7(28+x) \Rightarrow 324-9x=196+7x \Rightarrow \\ \\ ~~~~~~~~~~~~~~~~~\Rightarrow -9x-7x=196-324 \\ ~~~~~~~~~~~~~~~~~-16x=-128 \\ \\ ~~~~~~~~~~~~~~~~~~~x= \frac{-128}{-16} \\ \\ ~~~~~~~~~~~~~~~~~~~~~\boxed{x=8}$