Hello!
When you subtract these numbers, you always first subtract the numbers in the smallest place value. In this case, that would be the .5 and .7. However, since you cannot subtract 7 from 5 without getting a negative number, borrow a one from the place value that is one greater.
Thus, you get:
15 - 7 = 8
Therefore, we know that the ._ digit of our result is .8.
Now, moving on to the next smallest place value (in this case the largest).
You would subtract 7 - 3, however remember earlier that we borrowed a one. When you borrow a one, you must subtract one from the number that it was borrowed from. Therefore, the equation would become 6 - 3.
6 - 3 = 3
Therefore, the ones digit of our result is 3.
Put these two together, and you get your result of 3.8.
Hope this helps!
