Answer:
(x, y) = (- 3, 3)
Explanation:
given the 2 equations
- x + 3y = 12 → (1)
y = 6x + 21 → (2)
Substitute y = 6x + 21 into (1)
- x + 3(6x + 21) = 12 ← distribute
- x + 18x + 63 = 12
17x + 63 = 12 ( subtract 63 from both sides )
17x = - 51 ( divide both sides by 17 )
x = - 3
Substitute x = - 3 into (2) for y
y = (6 × - 3 ) + 21 = - 18 + 21 = 3
solution is (- 3, 3 )