The average of a list of numbers is their sum divided by the number

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

If m 17 27 90 63 ** picture is attached

Find the midpoint m of z1=(8+5i) and z2=(12+3i)