y^-9 * b = y^45 Divide by y^-9
b = [tex] \dfrac{y^{45}}{y^{-9}} [/tex]
The law of powers says that if you have the same base (y in this case) and two different powers that are divided, you can subtract the denominator from the numerator (in this case)
b = [tex]y^{45- - 9} = y^{54}[/tex]
