There are many ways a problem can be simplified. You can divide by the GCF (Greatest Common Factor) or even factor which depending on where you are in math you may or may not have learned. For your problem, I will use the first method.
3m-8 can be multiplied by any term (keep it simple):
2(3m-8) = 6m-16
4(3m-8) = 12m-32
Your answers should be 6m-16 and 12m-32.