Step 1: Write the second number under the first number so that the ones and tens places are lined up.

Step 2: Look at the ones column. 3 is less than 4, so take 1 ten from the tens place, change the ten to 10 ones, and add the 10 ones to the ones place. This is called regrouping.
Then, subtract the ones column (13 - 4 = 9). Write the 9 in the ones place of the difference.

Step 3: Subtract the tens column (6 - 4 = 2). Write the 2 in the tens place of the difference.