First, the formula for the average of a data set must be defined. It is calculated by adding all the numbers in the data set and then dividing the sum by the number of data. In this case, the average is set to be equal to $400 with the total number of data being 3, with the September expenditure set as an unknown, x. The equation is then set-up to be: 400 = (401.5 + 250 + x)/3. Thus, Joshua can spend as much as $ 548.5 to be able to have the same average as in his second quarter expenditure.
