[求助]prep一道数学题

zonderss

The points A, B, C, and D are on a numer line, not necessarily in that order. If the distance between A and B is 18 and the distance between C and D is 8, what is the distance between B and D?

1) The distance between C and A is the same as the distance between C and B

2) A is to the left of D on the number line.

为什么答案会是E呢？

完全不明白。。。陷入困境~

请教各位大侠

taoyeye

条件一告诉了C在A，B中间，条件2告诉了A在D的左边。仍然不知道D更靠近A一些，还是更靠近B一些。BD的距离1和17都是可能的

zonderss

恍然大悟。。。

THX~~

唉。。怎么感觉一碰到考试脑筋就揪成一团。。然后就不灵光了。。