If a = −4, and b = 3, what is |a − b|?

The vertical bars surrounding a − b designate the absolute value of the difference. The absolute value of an expression is the distance from the simplified expression to 0; absolute value is always positive. Substitute the given values of a and b into the expression, evaluate the difference, and then apply the absolute value to make it positive.
|a − b|
= |−4 − 3|
= |−7| = 7
Recall that −4 − 3 is equivalent to −4 + −3 = −7