What is the difference between mathematics and

What is the average rate of change for this function for the interval from x=2 to x=4 ?

Suppose i flip two identical coins. what is the probability that i get one head and one tail?

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is