Era had 5 burgers for her and her 4 friends. She sliced each burger into halves. The first and second friends got 1 and 2 slices, respectively. Then the third and fourth friends got 3 slices each. How many slices of burgers are left for Era?
There are 5 x 1/2 = 10 halves of burgers made from 5 whole burgers.
Era's first and second friends got 1 + 2 = <T>add(1, 2)=3 slices together.
Her third and fourth friends got 3 + 3 = <T>add(3, 3)=6 slices together.
Era's four friends got 3 + 6 = <T>add(3, 6)=9 slices.
So, Era is left with 10 - 9 = <T>subtract(10, 9)=1 slice.
