Answer:
The three-dimensional formula that would give you the required result, that is suming the diesel fuel expenditures, which are always recorded in cell D18 for the months of August through December is:
=SUM(August:December!D18).
Step-by-step explanation:
First, enter the excel starting formula "=SUM(". Type "August" or left-click on the August sheet with the mouse. Type in colon and December or hold the Shift key and left-click on the December sheet. Then, select the cell C3 in the December sheet. Before pressing "Enter," add a closing bracket. The sum formula looks exactly like this: "=SUM(August:December!D18)." This formula can completely be typed manually. The formula sums up cell D18 across each of the sheets from August to December, returning a value.