Answer
80 - 73 = 7
Work Step by Step
80 - 73
Subtract the ones column. Since 0 is less than 3, borrow from tens column and compute 10 - 3. Write 7 in the ones column of your result.
Subtract the tens column, SInce you borrowed from the tens column in the previous step, compute 7-7. The result is zero so write nothing in the tens column.