We probably want to get this into standard form (ax^2 + bc + c = 0). Our first step is to distribute the y into the parentheses:
y^2 - 9y = - 18
Now add 18 to both sides:
y^2 - 9y + 18 = 0
Factor. In order to do this, find two factors of 18 that add to -9. These would be -6 and -3. We can now rewrite the equation as binomials:
(x - 6)(x - 3) = 0
Solve both separately:
x - 6 = 0
x = 6
x - 3 = 0
x = 3
Your two solutions are x = 6 and x = 3.