Answer:
AB = 7
Step-by-step explanation:
The polygon pictured is a hexagon, which means that it has 6 equal side lengths. The perimeter is 42. AB is the length of one side.
Perimeter = 6 x length of one side
If you plug everything you know in the equation, you would get...
42 = 6 x length of one side
42 ÷ 6 = 7
So, 7 is the length of AB, since in a hexagon, all sides are the same length.