Excel can solve for unknown variables, either for a single cell with Goal Seek or multiple cells with Solver.

How to Use Variables in Excel. Knowing how to use Excel's variables gives you the ability to make your formulas – and by extension the spreadsheets containing those formulas – much easier to ...

Single-variable equations are among the easiest to construct when using this tool. Use the Equation Editor to insert an equation into any cell in your Excel worksheet.