Is there some other part of this ?
If you times 39.99 by 0.20 (20%) then you get your answer of $7.99
They are opposites. since |-3| has the lines around it, this represents absolute value, which is not positive or negative but how far away the value is from 0. the plain -3 remains the same. |-3| is 3, because it is 3 units away from 0 on the number line.
These are called integer numbers.
We start with natural numbers (or whole numbers), i.e. the set

When you add the opposite of each whole number, you have the set of integers:

Answer:
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Step-by-step explanation:
4+8*12=45