To me, the formula one might need are:
1. =SUM(C5:C7)/C4
2.=SUM(C5:C7)/$C$4
3. =SUM(C5:F5)/B$5
So, one need to know that to enter a formula in cell C9 that divides the sum of cells C5 through C7 by cell C4 and uses absolute cell references,
One can also use the following formula: =SUM(C5:C7)/C$4
In the above formula, the $ symbol before the cell reference C4 indicates that it is an absolute cell reference. This means that when you copy the formula to cells D9:F9, the cell reference C4 will not change. SUM(C5:C7), This part of the formula sums the values in cells C5, C6, and C7.