Answer:
x = 4 , y = -1
Step-by-step explanation:
x - 3y = 7 -- (1)
3x - 3y = 15 -- (2)
Rewriting (1), x = 3y + 7 -- (1)'
Substituting (1)' into (2),
3 ( 3y + 7 ) - 3y = 15
9y + 21 - 3y = 15
6y = -6
y = -1 -- (3)
Substituting (3) into (1),
x - 3 ( - 1 ) = 7
x + 3 = 7
x = 4 -- (4)
According to (3) and (4),
x = 4 , y = -1
