Answer:
x = 3
Explanation:
Since the points are collinear, the Segment Addition Postulate says that the sum of AB and BC equals AC:
AB + BC = AC
Thus, we can now find by substituting x + 7 for AB, 2x for BC and 16 for AC:
x + 7 + 2x = 16
(3x + 7 = 16) - 7
(3x = 9) / 3
x = 3
Thus, x = 3.