Answer
$13$
Work Step by Step
First, recall that $a-(-b)=a+b$
$=-7 +20$
The numbers have the opposite signs, so subtract the smaller absolute value from the bigger absolute value, and then apply the sign of the addend with the higher absolute value to the answer. Thus, we obtain:
$
\\=|20|-|-7|
\\=20-7
\\=13$
