Answer:
x=8, y = 0
Explanation:
Substitution is easier for this problem.
3x + y = 24 ---> y = 24 - 3x
x^2 + y = 64
Substitute y
x^2 + 24 - 3x = 64
x^2 - 3x = 40
Factor out x
x(x-3) = 40
Pretty much you can guess and check
x = 8
If x = 8, y = 0
or
x^2 - 3x = 40
Complete the square
x^2 - 3x + 2.25 = 42.25
(x-1.5) ^2 = 42.25
Square root both sides
x - 1.5 = 6.5
x=8
x - 1.5 = -6.5
x = -5
Check
x = -5 doesn't work, so x = 8 and y = 0