Mathematics in the second grade of primary school has just moved from step by step to comprehensive calculation. At first, students were always uncomfortable, so they made such mistakes. Don't worry, students will naturally understand after practicing a few more times. As long as they master the operation sequence, they won't make any more mistakes. When you need to calculate the priority, put parentheses.
The rule of calculation is: from left to right, multiply first and then divide, then add and subtract. Sometimes it is necessary to upset such rules. For example, what should I do if I need to add and subtract first? You need to put the parts that need to be added or subtracted in brackets first, so that you can calculate the addition and subtraction first.