Use the distributive property to remove the parentheses.
5b^3(6b^2-4)

Step-by-step explanation:

The distributive property says:

for every a, b, c, (the distributive property over addition)

or (the distributive property over subtraction).

In your case, applying distributive property over subtraction to the expression , you get

if you mean

then it's c. 8, -7/3

but if you mean

then it is