when subtracting and you run out of numbers to take from what do you do?

TRY WATCHING THIS CLIP

 

https://www.khanacademy.org/math/arithmetic/addition-subtraction/sub_borrowing/v/basic-regrouping-or-borrowing-when-subtracting-three-digit-numbers

If you mean:  what do you do when you are subtracting a larger number from a smaller number ---

For example:  How much is  345 - 789 ?

Reverse the problem:  789 - 345  to get  444 and attach a negative sign, because your answer is a negative number:         345 - 789  =  -444

For example: 125-247=? To do this you must end up with a negitive number as we can see we already don't have enough to take away 247 so here's what to do.

Let's start with our last number's, 5-7= -2

2-4=-2

1-2= -1

Now we can put our numbers in order, -122 If you noticed all of the answers were negitive so that means your number will be a negitive.