Answer:
The answer is no because for 1 hour he gets 20 dollars and for 2 hours he gets 30$ (which is less for working 2 hours). So, if you multiply 2 hours with 20 dollars, you should get 40, not 30. So therefore, it is not proportional. And same for 3 hours: multiply 3 with 20 to get 60, not 50.