18
I used a calculator so you’ll need someone else to explain my apologies. I’m tried but I wanted to try and help by giving you the answer
Answer:
b = -6
Step-by-step explanation:
Apply the exponent rule that
In this case, 
Set that equal to
:

Apply the exponent rule that
so now you get:

Since the base is y for both sides of the equation, just set the exponents equal to each other and solve for b.
4b = -24
divide each side by 4 to get:
b = -6