(1) has no hints of curly braces and small question marks, and there are no hints of dotted lines and diagonal lines. Usually, you write an addition formula. If there are two formulas left in the topic, write two addition formulas: one from left to right and the other from right to left. as follows

If it is two, it can also be written as 5+7= 12.

(2) This kind of question is prompted by braces and small question marks, and it is clear what the problem is. So generally, according to the topic, you can choose the appropriate formula, so just write one.

Braces indicate the total number of several parts.

When the question mark is at the tip of the braces, you will usually find out how many * * * the left and right parts add up to.

The second category: subtraction problem

(1) This kind of problem is clearly explained, and the dotted line and diagonal line both mean to take away and move away. Here, the part occupied by the imaginary coil and the part crossed diagonally indicate that a part has been removed from the total. In this case, only one formula can be written, but it must be emphasized that the total number of objects must be reduced. Some students can easily use the rest to write the part they took away. Examples are as follows:

10-4=6

(2) This kind of question is reminded by braces and small question marks. As long as you pay close attention to what the question asks (sometimes you ask how much the left part is, sometimes you ask how much the right part is), you will understand it easily.

The method is: first find out what the total is, and then remove the side without a small question mark.

But there are still many students who can't understand that subtraction is always written as addition. At this time, you should ask questions to guide you, such as:

Some apples are put in the basket and some are put outside. We know that there are 12 apples in total. There are two apples outside now. How many are there in the basket?

The third kind of problems: continuous increase and continuous decrease.

Question 1: 6 on the left, 5 in the middle and 7 on the right. How many sticks are there in all?

Question 2: There are *** 18 sticks in total. Take away 5 sticks and 7 sticks. How many sticks are left?

The fourth category: addition and subtraction mixed questions, which need to be understood.

The first question can be understood as follows: the bus arrives at the station. There were eight people in the car. At this time, four people get on the bus, 1 get off. How many people were on the bus at that time?