Advice in solving uneven subtraction : Using the example you provides above- 31-12. The challenging dilemma in solving this mathematical problem that we first notice ( make sure problem is written on paper and aligned properly so you can be sure to solve it correctly) 1 can't subtract 2. So what do we do? This is when it is important to learn that in this case( and in every mathematical problem you will ever solve that is uneven, what I am telling you it is important to remember) there is a 3 next to the ones. Important fact: The way the numbers are lined up 31 is three tens and 1 one. 12 is one tens and 2 ones. So since you dont have enough ones to subtract 2 you should borrow from your tens ( in this problem it is 3 tens, once you borrow a tens for the one, there will be only 2 tens). So now on paper this is how your problem should look so far : 31-12( 3 has now became a 2, because you borrowed 1 from the tens group, 1 has now become 11 because of the 1 tens you borrowed. Now you are simply ready to complete the subtraction of this mathematical problem! ( That uneven has now become 11-2, which is possible to subtract and that equals 9. And 2-1 equals 1. So now you have your answer, which should be 19. Another interesting fact: Whenever you have a subtraction problem like this, remember you can always check it to be correct by adding your answer to the second number you subtracted. For instance: 19+12=31, so we know this problem was solved correctly.
