if you have 70 calls that come in during one minute and 3 seconds..and then you have 10 calls come in at a total of 15 seconds. what is the weighted average of calls and time?

Question

I assume you want the weighted average of the frequency of receiving calls. The easiest way to get this is to divided the total number of calls by the total time interval,
Avg. call rate = 80 calls/78 s
1.026 calls/sec

You would get the same average by first computing the call rate in each interval (1.270 and 0.667 calls/s) and then computing a weighted average using the length of the interval as a weighting factor.