Need with solving quadratics using the quadratic equation! see image, this is a word problem.

You need to solve the following equation:
-0.5x^2 +36x -161 = 451

Set right side to 0
-0.5x^2 +36x -612 = 0

Multiply by -2 to get rid of decimal and leading neg coefficient.
x^2 -72x + 1224 = 0

Use quadratic formula:
a = 1, b = -72, c = 1224



Therefore the min price to have 451 profit is $27.51