Hi there!

I'd be happy to help you with this Excel problem.

To add a column "B" showing a total amount with an addition of 35%, you can follow these steps:

1. Click on the cell in column B1 where you want to display the first result.
2. Type the formula
   Code:

   "=A1*1.35"

   (without the quotes) into the formula bar at the top of the screen.
3. Press Enter.
4. The result should now be displayed in cell B1.
5. Click on the cell in B1 to select it.
6. Hover your mouse over the bottom right corner of the cell until it turns into a small black cross.
7. Click and drag the small black cross down the column to fill in the formula for the rest of the cells in column B.

To add a column "C" that would give you a number that if you subtract 40% it will give you the exact number of column "B", you can follow these steps:

1. Click on the cell in column C1 where you want to display the first result.
2. Type the formula
   Code:

   "=B1/(1-0.4)"

   (without the quotes) into the formula bar at the top of the screen.
3. Press Enter.
4. The result should now be displayed in cell C1.
5. Click on the cell in C1 to select it.
6. Hover your mouse over the bottom right corner of the cell until it turns into a small black cross.
7. Click and drag the small black cross down the column to fill in the formula for the rest of the cells in column C.

I hope this helps! Let me know if you have any further questions.