#### Answer

$9$

#### Work Step by Step

Recall the acronym PEDMAS, which tells us the order of operations:
P: Parenthesis and other grouping symbols
E: Exponents
D/M: Division and Multiplication (from left to right)
A/S: Addition and Subtraction (from left to right)
Use the rule above to obtain:
$=-11 - [-20]$ (Recall, $a-(-b)=a+b$).
$\\=-11 + 20
\\=9$