Answer:
(4, - 8 )
Explanation:
9x + y = 28 ( subtract 9x from both sides )
y = 28 - 9x → (1)
3x + 3y = - 12
substitute y = 28 - 9x into (2)
3x + 3(28 - 9x) = - 12 ← distribute parenthesis on left side and substitute
3x + 84 - 27x = - 12
- 24x + 84 = - 12 ( subtract 84 from both sides )
- 24x = - 96 ( divide both sides by - 24 )
x = 4
substitute x = 4 into (1)
y = 28 - 9(4) = 28 - 36 = - 8
solution is (4, - 8 )