The important rule of addition (“plus-calculation”) is:

$\text{summand} + \text{summand}$ $= \text{sum}$

At addition, the operands are designated as summand. The sum is the result.

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### The sign

• If the summands have the same sign, you set the common sign and add the contributions.

• If the summands have different signs, you set the sign of the larger summand and subtract the smaller amount from the larger one.

### Examples

• #### Set the common sign and add the contributions

$(-5)+(-3)=-(5+3)=-8$
$(+3)+(+6)=+(3+6)=+9$
• #### Set the sign of the larger summand and subtract the smaller amount

$(-8)+(+3)=-(8-3)=-5$
$(+7)+(-9)=-(9-7)=-2$
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### Mathematical laws

If $a$, $b$ and $c$ are rational numbers, you have to consider these following mathematical laws: