Answer:
20 units
Explanation:
Chords the same distance from the center have the same length, so ...
AB = DE
3x -7 = 5(x -5)
3x -7 = 5x -25 . . . . . eliminate parentheses
18 = 2x . . . . . . . . . . . add 25-3x
9 = x . . . . . . . . . . . . . divide by 2
AB = 3x -7 = 3(9) -7 = 20
The length of AB is 20 units.