Question

determinati numerele x si y stiind ca 2x+5y supra 3x-2y = 15 supra 13 si x+y=12

Answer 1

$\frac{2x+5y}{3x-2y} = \frac{15}{13}$
x+y=12⇒x=12-y 
$\frac{2(12-y )+5y}{3(12-y )-2y} = \frac{15}{13}$

[2(12-y )+5y]×13=[3(12-y )-2y]×15
[24-2y+5y]×13=[36-3y-2y]×15
312+39y=36×15-5y×15
312+39y=540-75y
104y=540-312
104y=228
y=228:104=114:72=57:36
y=57/36
x+y=12⇒  x=57/36-12
x=375/57