Answer
$-2$
Work Step by Step
The order of operations follow the following degree of priority (PEMDAS rule):
First Priority:
Parentheses and grouping symbols
Second Priority:
Exponents
Third Priority:
Multiplication or Division, whichever comes first from the left
Fourth Priority:
Addition or Subtraction, whichever comes first from the left
Use the rule above to find:
$=-20-(-18)
\\=-20+18
\\=-2$