Answer:
40 minutes
Step-by-step explanation:
You can simply make 200/5 = 40 5 minute calls per month.
This works because every call is a 5-minute call. So then we just have to find how many times we can make a 5-minute call up to 200 minutes. We already have an operation for this: Division. This acts as the opposite of multiplication and speeds our process up.
