So you need to do 3 things.
First, find craigs distance by adding up the sides.
1)
C = 42 + 56 = 98
Then, find the direct distance, D. This can be done using Pythg. Theorem.
2)
D = √(42²+56²) = 70
3) Now just find the difference.
A = 98 - 70 = 28
A = 28!