Answer:
10 units
Explanation:
the longest length is from (11, 1) to (3, 7) and can be clearly shown when graphed
now to find the length you must use the pythagorean theorem
the distance between 11 and 3 is 8 and the distance between 1 and 7 is 6 so
8^2 + 6^2 = c^2
64 + 36 = c^2
100 = c^2
c = 10
that is your answer