求助一道PREP数学题目

xianyun543

Of the 75 houses in a certain communit, 48 have a patio, How many of the houses in the community have a swimming pool?

1) 38 of the houses in the community have a patio but do not have a swimming pool.
2) The number of the houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio.

答案是 B, 但是我怎么做从2）中也推不出来，请帮忙看一下，谢谢。

lifery

这道我今天做也错了哈~~
先假设有have patio and swimming pool的人数是x，那么have neither a SP nor P的也是x，仅有SP的是y，仅有P的是z。
这样我要求的也就是x+y。
我们已知：48=z+x，75=x+y+z+x。俩一减就得出来x+y啦~也就是27~

xianyun543

对，我一门心思要找只有Swiming pool没有 Patio的，想偏了。。谢谢。