Answer:=(C15-C17)/C17
Explanation: First step is to get the difference between the total donation amount and the projected donation amount. This is done as follows: (C15-C17). It was put in parentheses so that the software calculates this first before dividing.
The next is to divide the result by the projected donation amount with C17 as its cell reference. This means the input should be (C15-C17)/C17
Note: Entering the formula without the parentheses (e.g. C15-C17/C17) simply means deducting the projected amount (already divided by the projected amount) from the total donation amount