In this case, Excel has been set, and the setting is to display only the formula in the cell, not the result. There are two solutions:
1 Use the shortcut key CTR+~
2 Click the " Formulas " tab, and then deselect the " Show Formulas " button inside (this is the Excel 2013 method, other versions may have different button positions, but the shortcut keys are still easy to use)