(1+2) What do you mean?

This is a mathematical addition operation: 1+2=3.

The addition operation here is in parentheses, which has the right of priority calculation, for example, (1+2)×3. Although there is multiplication, parentheses have higher priority than multiplication, so the calculation inside parentheses comes first and then outside.

Addition (usually indicated by the plus sign "+") is one of the four basic arithmetic operations, and the others are subtraction, multiplication and division. For example, in the picture below, * * * has a combination of three apples and two apples, and * * * counts as five apples. This observation is equivalent to the mathematical expression "3+2 = 5", that is, "3 plus 2 equals 5".

Extended data:

Addition is written with the plus sign "+"between terms; The result is represented by an equal sign. For example,

In other cases, even if no symbols appear,

Fractions followed by numbers represent mixed numbers. For example,

This symbol may be controversial because in most other contexts, two numbers together represent multiplication.

The sum of a series of correlation numbers can be expressed by σ symbol, indicating iteration. For example,