Question

resolver o sistemas
x=3y
x-y=10

Answer 1

x-3y=0
x-y=10 (×-3)

x-3y=0
-3x+3y=-30
__________
-2x=-30 (x -1)
2x=30
x=30/2
x=15.
___________
x-3y=0
15-3y=0
15=3y
y=15/3
y=5.