Subtract

Explanation

As we prepare to subtract in each column, we will compare the digit in the subtrahend (bottom number) to the digit directly above it in the minuend (top number).  If a digit in the subtrahend is greater than the digit directly above it in the minuend, we must borrow (regroup) to subtract in that column.

To help you understand the process, each step of this subtraction is explained separately.  Your solution need only look like the last step.  We write the subtraction in vertical form to line up the tens digits and line up the ones digits.

\(  \begin{array}{r} \phantom{-}\,32 \\ -\underline{15} \\[4pt] \phantom{-}\,17 \end{array}  \)

Since 5 in the ones column of 15 is greater than 2 in the ones column of 32, we cannot immediately subtract in that column because 2 - 5 is not a whole number.  To subtract in the ones column, we must regroup by borrowing 1 ten from 3 in the tens column. In this regrouping process, we use the fact that 1 ten = 10 ones.