If the missing number is a minuend or subtrahend, students use the count back strategy or the relationship between addition and subtraction to find the missing number. And if the missing number is the difference of the subtraction sentence, they subtract the numbers to get the sum. This worksheet, subtract two multiples of 10, provides plenty of practice with this concept. As the worksheet uses a horizontal format, it allows for more creativity when it comes to how the student solves the problem. In contrast, in the vertical format, students usually employ the standard method to solve.