Sometimes the easiest way to carry out a subtraction sum is to count up from the lower number. This is especially true if the two numbers are close to each other, but cross the tens boundary. A subtraction such as 41 - 37 could be done in this way. Count on 3 to 40 and then 1 more to 41, making the answer 4. I have seen children so confused by number that they get their pencil and paper out, write out the sum with the numbers under each other and then attempt the standard written method - all for something they could easily do 'in their head'! Subtracting 2-digits by counting up