-30x - 20: We can see that both numbers have a factor of -10, because 30 and 20 are multiples of 10 and -30x and -20 are both negative. So the factored form is -10(3x + 2).
12x - 28: The greatest common divisor of the two numbers is 4, so the factored form is 4(3x - 7).
-10x - 5: Like the first problem, the biggest factor is -5, so the factored form is -5(2x + 1).
