A. Spell checker, because it tells you wants wrong with your version and what you might have meant to say.<span />
You can explain this subtraction from many different aspects. One of them could be just working with these given numbers when we increase them proportionally, final answer also increases proportionally. For example,
16 - 7 = 9
9
160 - 70 = 90
If we add the final results to the subtracted number, we will get the number itself. For example,
16 - 7 = 9
16 = 7+ 9
value....................
Hm, I will ask my dad this and I will report back to you!!!
