1. tells you that |x + 3| = 14, which means that:
a. x + 3 = 14, when you get x = 11
b. x + 3 = -14, when you get x = -17
Then calculate |x + 7| for both cases:
a. x = 11 --- |x + 7| = |18| = 18
b. x = -17 --- |x + 7| = |-10| = 10
You get two answers, so IMHO A isn't sufficient.
2. means that (x + 2)^2 = 169 = 13^2 = (-13)^2 - this is why you have two cases as well:
a. x + 2 = 13 --- x = 11 --- |x + 7| = |18| = 18
b. x + 2 = -13 --- x = -15 --- |x + 7| = |-8| = 8
Again, you get two answers.
But put both stmts together to get single answer 18. This is why the answer is IMHO C.