Question

Na proporrçao x/5=y/7 calcule o valor de x e y sabendo q x+y=18

Answer 1

Boa noite

$\frac{x}{5}\;=\; \frac{y}{7}$

5y = 7x

$y\;=\; \frac{7x}{5}$

x + y = 18 

$x\;+ \frac{7x}{5}\;=\;18$

mmc = 5 

5x + 7x = 90

12x = 90

$x\;= \;\frac{90}{12}$

$x\;=\; \frac{15}{2}$

$y\;=\;18\;-\; \frac{15}{2}$

$y\;=\; \frac{21}{2}$

$x\;vale\; \frac{15}{2} \;e\;y\;vale\; \frac{21}{2}$

Answer 2

{x/5=y/7
{x+y=18

{7x-5y=0
{x+y=18----> *5


{7x-5y=0
{5x+5y=90
----------------
12x=90
x=90/12--->15/2


x+y=18

15/2+y=18

y=18-15/2

y=21/2

(X, y)=(15/2 , 21/2)