Evaluate 100-15

Set up the subtraction problem in long subtraction format.

Borrow ${\displaystyle 10}$ from the digit in the next column to the left. Add the borrowed ${\displaystyle 10}$ to ${\displaystyle 0}$. Reduce the number that was borrowed from by ${\displaystyle 1}$.

Subtract ${\displaystyle 5}$ from ${\displaystyle 10}$.

Borrow ${\displaystyle 10}$ from the digit in the next column to the left. Add the borrowed ${\displaystyle 10}$ to ${\displaystyle -1}$. Reduce the number that was borrowed from by ${\displaystyle 1}$.

Subtract ${\displaystyle 1}$ from ${\displaystyle 9}$.

Subtract ${\displaystyle 0}$ from ${\displaystyle 0}$.