I'm not sure if I'm interpreting what you need correctly without more information.
If 3 is also degree:
x= unknown #
Set up a proportion. 2 is to 20 as 3 is to x.
2/20 = 3/x
cross multiply
(2*x) = (20*3)
2x= 60
divide both sides by 2
x= 30
2 degrees= 20
3 degrees= 30
Hope this helps! :)
