With the sheets grouped, apply Underline to cell B5 and Double Underline to cell B6. Ungroup the worksheets. Note, use the Format Cells dialog box to ensure that the Underline styles Single and Double are applied, rather than Single Accounting or Double Accounting.

Check Explanation.

Explanation:

Task: (1). Apply Underline to cell B5 and Double Underline to cell B6.

(2). Ungroup the worksheets.

(3).use the Format Cells dialog box to ensure that the Underline styles Single and Double are applied, rather than Single Accounting or Double Accounting.

Steps to follow;

Step one: On the Excel document that you are working on, make sure you highlight from B6 cell to F6 cell.

Step two: Then, press CTRL+SHIFT+F.

Step three: from action in step two above, the "format cells dailogue box" will come up, click underline > (underline type) dropdown list > ok.

Step four: next, highlight from B7 to F7.

Step five: press CTRL+SHIFT+F. As in step two above.

Step Six: do the same thing as in Step three above.

Please note that to apply the SINGLE UNDERLINE, you need to type the data in the cell for cells of B6 to F6 ONLY.

Also, for DOUBLE UNDERLINE for B7 to F7; just type the data in the cell and it will apply.