Google Sheets In Pictures

By employing an absolute reference—using the $ symbol to make each formula use the same cell containing the frog price—the formula stays accurate for all months.

15 Edit the formula in cell B5 in the Revenue sheet...

...to make cell G6 in the Numbers Per-Frog sheet an absolute reference.

16 Use the Fill Handle to copy the formula in cell B5...

...so the Revenue sheet shows each month's net revenue.

When you're done, the Revenue sheet should look like this: