Question

(08.05)

Answer 1

I: x-3*y=12
II: 2*x+6*y=60

add I*2 to II:
2*(x-3y)+2x+6y=2*12+60
2x-6y+2x+6y=24+60
4x=84
x=21

insert x=21 into I:
21-3y=12
9-3y=0
9=3y
3=y


is the only solution (21,3), sou you probably have another option which you didn't copy :)