Question

calcule x e y na proporção $<var>\frac{x}{y} = \frac{3}{4}</var>$  , sabendo que x + y = 35

Answer 1

$\frac{x}{y} = \frac{3}{4} \\\\x= \frac{ 3y}{4}$

sabendo que x vale 3y/4
substitui x na outra equação
$x+y=35\\\\ \frac{3y}{4}+y =35\\\\ \frac{3y.1 +y.4}{4} =35\\\\ \frac{3y+4y}{4} =35\\\\ \frac{7y}{4} =35\\7y=35.4\\\\7y=140\\\\y= \frac{140}{7}=20$

y vale 20

x+y = 35
x+20 = 35
x=35-20
x=15

x=15
y=20