What is something that multipys to 72 and adds -27?

24 if you look at a factor tree, -24 x -3 = 72 and -24 + -3 = -27

You want xy=72 and x+y=-27. Now solve for either x or y in one of the equations and then substitute it into the other equation. For instance, x=-27-y so you can substitute to get (-27-y)y=72. Distribute so -27y-y^2=72. let's move everything to one side so 0=y^2+27y+72. Now use quadratic formula to solve.