# Answer check — episode 82

The untouched sample total is 150. In a workbook copy, =SUM(B2,C2,D2) becomes a #REF! formula after deleting February column C. Immediate Undo restores the February 50 and the 150 total. Rewriting the formula without restoring the month would yield only 100, which is not the intended recovery.

## Applicability

Undo is the demonstrated path immediately after the deletion. A saved, closed, or edited workbook may require version history or a backup; this guide does not promise reconstruction from #REF alone. Deleting an entire sheet has different recovery limits.

The practice example is fictional. Confirm the current control and result in your own permitted English-language application copy.