Answer:
15wz² - 2wz³
Explanation:
when collecting like terms the terms must have the same variables, with variables having the same exponents.
(15wz² + 3wz³) - 5wz³ ← remove parenthesis
= 15wz² + 3wz³ - 5wz³ ← collect like terms
= 15wz² + (3wz³ - 5wz³)
= 15wz² + (- 2wz³)
= 15wz² - 2wz³