Select the cell where you want the result.
Enter `=` followed by the first value or cell reference.
Type `-` (minus).
Enter the second value or cell reference.
Press `Enter`.
Example (two cells): `=A1-B1`
Example (range subtraction): `=SUM(A1:A5)-SUM(B1:B5)`
Example (subtract a number): `=A1-10`
Example (subtract from a number): `=10-A1`
Copy the formula to other rows/columns as needed (cell references adjust automatically).