There are many ways of calculating 725-96. Use whatever suits you best. Here's one.
You have a chest of 3 drawers. In the top drawer marked “hundreds” you put in 7 large boxes. In each of these boxes there are 10 smaller boxes marked “tens”.
In the next drawer marked “tens” you have 2 smaller boxes marked “counters”, each containing 10 counters.
In the bottom drawer marked “counters” you have 5 counters.
The 3 drawers represent the number 725.
Now you're going to take away 96, that's 9 tens and 6 counters.
Go to the tens drawer and open it. You can't take 9 boxes out of it because there are only 2. Go to the top drawer and take out one large box. That leaves 6 in the top drawer.
Open the box and put the 10 smaller boxes in the tens drawer. Now you have 12 small boxes, enough to take away 9, leaving 3.
You need to take 6 counters out of the bottom drawer, which only contains 5. Open the tens drawer and take out a small box and empty its 10 counters into the bottom drawer, so now you have 15 counters in the bottom drawer, but only 2 small boxes in the middle drawer.
Take away 6 counters from the bottom drawer leaving 9.
Open all the drawers. How many boxes and counters altogether? 6 in the top drawer and 2 in the middle. In the bottom drawer there are 9 counters. So we have 629 in our chest of drawers. That's the answer.
3÷0: How many times can you take zero from 3? You can never take enough, so you can't divide anything by zero.
Add 3 counters to 5 or 5 counters to 3 and the answer, 8, is the same.
