Answer:

You just need to think about this a little. There is a number, that you don't know, x, and if you square it (x^2), that value will be equal to 72 more than the unknown number itself, so you put that into an equation.

Step-by-step explanation:

x^2=x+72
x^2-x-72=0

Apply quadratic formula (you can look it up)

x_1=\frac{-(-1)+\sqrt{(-1)^2+(-4*1*-72} )}{2(1)}
x_2=\frac{-(-1)-\sqrt{(-1)^2+(-4*1*-72} )}{2(1)}

There are two answers to the quadratic formula.

The rest should be easy.