Answer:
AB = 21
Step-by-step explanation:
The midpoint divides the segment into two congruent parts, so you have ...
AB = BC
x +5 = 2x -11 . . . substitute the given expressions for AB and BC
16 = x . . . . . . . . add 11-x
Then the measure of AB is ...
AB = x +5 = 16 +5 = 21