Answer: -10, -8
Why:
X^2 + 18x + 80 = 0
(X + ?) (X + ?) = 0
Two numbers that add to equal +18 and multiplies to equal +80 are 8 and 10
(X + 8)(X + 10) = 0
Now we can separate what is in the parentheses into possible cases
X + 8 = 0
X = -8
X + 10 = 0
X = -10