He can sum 2 to 2 and find the right awnser.
Oh and by the way, just in case you don't know, he's a lucasian professor.
Yes I know he's a professor.
Hawking has made revolutionary answers on the bigger questions like:
Where do we come from? How did the universe begin? Why is the universe the way it is? How will it end? Some of his equations are so intricate and ingenous that most people can't even begin to fathom it's true potental. 2+2? gtfo.