#### Answer

$-10$

#### Work Step by Step

Absolute value is used to represent the distance of a number from $0$ on a number line. Since distances are always positive, the result of an absolute value will always be positive. Therefore, to take the absolute value of a negative number, we simply take the negative of that number to make it positive, and to take the absolute value of a positive number, we do nothing to the number. Let us simplify the absolute value, and then subtract: $$10-|-20|=10-20=-10$$