Charles bought 20 papers to draw. Today Charles drew 6 pictures. Yesterday he drew 6 pictures before going to work and some pictures when he came back. How many pictures did Charles draw when he came back from work knowing that he has 2 papers left?
Charles drew 6 + 6 = <T>add(6, 6)=12 pictures.
He has 20 - 12 = <T>subtract(20, 12)=8 papers left.
So Charles drew when he came back from work 8 - 2 = <T>subtract(8, 2)=6 pictures.
