In a formula, there are only addition and subtraction or only multiplication and division.

In a formula, only addition and subtraction or only multiplication and division should be calculated from left to right.

Addition and subtraction are operations at the same level, and the operations have no order, so they need to be calculated from left to right, for example, 2+5-3-2=? In the order from left to right, calculate 2+5=7 first, then 7-3=4, and finally 4-2=2.

Similarly, the multiplication and division method is a hierarchical operation, and there is no order in the operation, so it needs to be calculated from left to right.

Extended data:

A comprehensive formula refers to a formula with addition, subtraction, multiplication and division at the same time, but at least one level (with two symbols):

Matters needing attention in comprehensive calculation formula (four operations):

1. If there is only addition and subtraction or only multiplication and division, it is calculated from left to right. For example, 2+ 1- 1=2, first calculate the number of 2+ 1, and then subtract 1 from the number of 2+ 1.

2. If primary operation and secondary operation exist at the same time, the secondary operation is calculated first.

3. If there are primary, secondary and tertiary operations (i.e. power, root and logarithm operations) at the same time, first calculate the tertiary operation, and then calculate the other two levels.

4. If there are brackets, count the numbers in brackets first (no matter what level, count first).

5. The third level should be counted in brackets, and then the second and first levels should be counted.