Click Solve and in the Solver Results dialog box, read the message at the top and the more detailed explanation at the bottom of this dialog.
If you define a >= constraint that specifies a lower bound different from zero for certain decision variable cells, it will take precedence over this option for those cells.
Select the Make Unconstrained Variables Non-Negative check box to specify that all decision variable cells without explicit lower bounds should be given lower bounds of zero.
In the Subject to the Constraints box, enter any constraints that you want to apply.
You can specify up to 200 variable cells. To have an effect, the variable cells must be related directly or indirectly to the objective cell, or to the cell reference in at least one constraint. Separate the nonadjacent references with commas.
In the By Changing Variable Cells box, enter a name or reference for each decision variable cell.
Using the Value Of option has the same effect as defining a constraint (see below) where the objective cell must be equal to the specified value. In this case Solver finds values for the decision variables that satisfy the constraints. You may leave the Set Objective box empty.
If you want the objective cell to be a certain value, click Value Of, and then type the value in the box.
If you want the value of the objective cell to be as small as possible, click Min.
If you want the value of the objective cell to be as large as possible, click Max.
The objective cell must contain a formula.
In the Set Objective box, enter a cell reference or name for the objective cell.
If you don't see it, you need to insert the Solver App. In the Excel Web App, the Solver Parameters dialog should be visible on the worksheet. If you don't see the Solver command (on the Data tab on Windows, or the Tools menu on Macintosh), you need to load the Solver Add-in. You can resize this dialog by selecting its lower right corner and dragging.
Click the Solver command to display the Solver Parameters dialog.