This is a question about quantity reduction. We can first calculate the original number of erasers, and then subtract the number of used erasers to get the remaining number of erasers. There are four erasers on the left and three erasers on the right.

According to the topic, add the rubber on the left and the rubber on the right to get the total number of erasers * * *: 4+3=7 erasers. It is known that 1 eraser is used. According to the calculation method of quantity reduction, the remaining quantity of erasers is 7- 1=6 erasers. So the answer after explanation is: there are 6 rubber skins left.

We know that there are four erasers on the left and three erasers on the right, so there are seven erasers in total. Then, we know that we used 1 eraser, which means that we have to subtract 1 eraser from the original 7 erasers. Subtract 1 from 7 and we get 6, so the number of erasers left is 6.

The method of learning subtraction:

1, understand the meaning of subtraction: subtraction is one of the basic operations in mathematics, which means that two numbers subtract one number to get another number. In order to understand the meaning of subtraction, we need to understand the relationship among the minuend, subtraction and difference. Minus minus minuend equals difference, that is, if we have an apple and eat one, how many are left?

2. Master the basic rules of subtraction: There are some basic rules of subtraction, such as subtracting a number equals to adding the reciprocal of this number. This rule can help us turn the subtraction problem into the addition problem, so that we can get the result more easily. In addition, we should pay attention to the problem of borrowing, that is, if a bit of the minuend is less than the corresponding bit of the minuend in subtraction, we need to borrow from the high position.

3, practice subtraction: learning subtraction requires a lot of practice. You can improve your calculation speed and accuracy by doing some exercises of addition and subtraction. In practice, we should pay attention to the diversity and flexibility of methods, such as using fingers, breaking ten, and leveling ten.

4. Cultivate good study habits: Learning subtraction requires patience and care, so it is necessary to develop good study habits. Pay attention to the examination and calculation when doing the problem, so as to avoid careless mistakes. At the same time, we should arrange the time reasonably to avoid excessive fatigue affecting the learning effect.