Find the sum and express it in simplest form. (-5y^3-7y-7) + (7y^3+8y)

Since the operation between the sets of parentheses is addition, we can just remove the parentheses all together and add like terms together to find the simplest form.

-5y^3-7y-7+7y^3+8y

(-5+7) y^3 + (-7+8) y-7

2y^3+y-7