Find the solution x = 3 + y 21x + 8y = -24

x = 0
y = -3

Explanation:
The first given equation is:
x = 3 + y > I
The second given equation is:
21x + 8y = -24 > II

Substitute with I in II and solve for y as follows:
21x + 8y = -24
21(3+y) + 8y = -24
63 + 21y + 8y = -24
29y = -24 - 63
29y = -87
y = -3

Substitute with y in equation I to get x as follows:
x = 3 + y
x = 3 + (-3)
x = 3 - 3
x = 0

Hope this helps :)