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
Let x= number of avocadoes she can buy
let y= total cost
y= 2x
9= 2x 9/2= 4.5
4.5= x
(you cannot cut the avocado in half therefore your answer is simply 4)