On Windows, Solver may be added in by going to File (in Excel 2007 it’s the top left Windows button) > Options > Add-ins, and under the Manage drop-down choosing Excel Add-ins and pressing the ...

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

Excel can solve equations through several of its mathematical functions, but the single Excel tool that works on the largest variety of equations is the program's Solver Add-in.

The popular Solver for Excel add-on has been redeveloped for Excel 2008 by Frontline Systems and Microsoft.

Solver is a linear programming / analysis tool for Excel that was included with Excel 2004 as an add-in, but dropped from Excel 2008 since it required Visual Basic for Applications (VBA).