Answer:
This is one of a variety of "subtraction solutions"--basically a different way to subtract by breaking numbers down into 10-digit chunks. It's not especially helpful for small subtraction problems, but as math gets more complicated, this method will come in handy.
Step-by-step explanation:
Here's an example: Jim had a bag of 15 jelly beans. He eats 8. How many jelly beans does he have left? Take apart the number to make a 10. Then subtract.
Here, you need to "take apart" the 8 to make your 15 jelly beans 10, then you subtract the remainder of 8 to get your solution. In other words,
--"take apart" 8 into 5 and 3 (because you're going to need a 5 to make 15 into 10). 15 minus 5 equals 10. HOORAY! You have your 10. Now, subtract the remaining 3. 10 minus 3 equals 7. Huzzah--your final answer!
On paper, the problem looks like this:
15 - 8 (5, 3) = ?
15 - 5 = 10
10 - 3 = 7
So...15 - 8 = 7
