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Negative numbers are numbers less than zero. They are represented with a minus sign (-) in front.
Examples include -5, -18.3, and -0.7.
In a number line, negative numbers are to the left of zero.

Negative numbers often describe conditions like debt or below-zero temperatures.
They follow specific rules in mathematical operations:
- When adding a negative number to a positive number, you essentially subtract the absolute value of the negative number from the positive one.
- Adding two negative numbers always gives a negative result.

The absolute value of a number is the distance between that number and zero on a number line.
It is always a positive number or zero.
Absolute value is denoted by vertical bars. For example, \(|-5| = 5\) and \(|5| = 5\).
The absolute value ignores the sign of the number; it's all about magnitude.

In our case, the absolute values are:
- \(|-18.3| = 18.3\)
- \(|22.1| = 22.1\)

Knowing how to find the absolute value is crucial for operations involving signed numbers, especially when determining differences between numbers with different signs.

Adding signed numbers requires understanding both the signs and absolute values involved.
Here are the basic rules:
- When adding two positive numbers, add their absolute values. The result is positive.
- When adding two negative numbers, add their absolute values. The result is negative.
- When adding one positive number and one negative number, subtract the smaller absolute value from the larger one. Assign the sign of the number with the larger absolute value to the result.

Applying this to our exercise:
- We have -18.3 (negative) and 22.1 (positive)
- Subtract \(|18.3|\) from \(|22.1|\): \(|22.1| - |18.3| = 3.8\)
- The number with the larger absolute value is 22.1, which is positive, so the result is positive
- Therefore, \-18.3 + 22.1 = 3.8\.