Of the 80 houses in a development, 50 have a two-car garage, 40 have an in-the-ground swimming pool, and 35 have both a two-car garage and an in-the-ground swimming pool. how many houses in the development have neither a two-car garage nor an in-the-ground swimming pool?

Total number of houses= 80
number of houses with two garage=50
number of houses with in-ground swimming pool=40
number of house with garage and swimming pool=35
thus number of houses with garage alone=50-35=15
Number of houses with in-ground swimming pool alone=40-35=5
Total number of house with atleast a garage of a swimming pool will be:
(35+15+5)=55

Number of house that have neither swimming pool nor garage:
80-55=25 houses