First, you would need to create an equation for this problem. Let x represent the unknown percent.

=

Next, you would cross multiply.
170x = 2,000
Now, all you would need to do is isolate the x. To do this, you would divide both sides of the equal sign by 170.
x =
11.7647058824%
20 is 11.7647058824% or, rounded, 12% of 170.
I hope this helps!