Question

Resolva os sistemas{3x+y=9 {2x+3y=13

Answer 1

I-{3x+y=9
II-{2x+3y=13 -> x=13-3y/2

II-3(13-3y/2)+y=9 -> 39-9y+2y=18 -> 7y=21 -> y=3
substituindo na primeira :
I-3x+3=9 -> 3x=6 -> x=2

Answer 2

3x+y=9
2x+3y=13
------------
y=9-3x
2x+3(9-3x)=13
2x+27-9x=13
-7x=-14
x= 2

y=9-3x
y=9-3.2
y= 3

tá valendo?
abraços!