Answer :
B- to solve the system, multiply the first equation by 3 and then add the result to the second equation.
I:2x-y=5
II:x+3y=0
I*3=6x-3y=15
I*3+II: 6x-3y+x+3y=15+0
7x=15
x=15/7
insert x=15/7 into II:
(15/7)+3y=0
3y=-15/7
y=-5/7
I:2x-y=5
II:x+3y=0
I*3=6x-3y=15
I*3+II: 6x-3y+x+3y=15+0
7x=15
x=15/7
insert x=15/7 into II:
(15/7)+3y=0
3y=-15/7
y=-5/7