To start, let's expand things out, as we cannot learn anything from this form. We get 30x + 20 - 10x + 4, or 20x + 24. To find the GCD (Greatest Common Divisor), we take the terms and try to find the number (or term) that divides them. It must be a constant, because of the 24, and 4 goes into 20 and 24. So, our final answer is 4(5x + 6).
