Tens and ones are the basic building blocks of subtraction. It makes subtraction a lot easier for the kids to learn. The concept is pretty simple. We have two categories, the tens and the ones.In a two-digit number, the number on the left side is the tens and the number on the right side is the ones. When you have to subtract two numbers, you put tens under tens and ones under ones of both numbers.So how does the kid learn this? Let’s make it simpler for them. You can draw a line with ten blocks and refer to it as tens, while the single blocks will be the ones. To subtract we will count the number of tens and the number of one's blocks in the picture and make a question. Similarly, the tens and the ones of the number which has to be deleted will be placed under the previous number respectively. And then we do the simple subtraction.