ALGEBRA
posted by MONICA .
From a survey of 100 college students, a marketing research company found that 70 students owned iPhones, 35 owned cars, and 25 owned both cars and iPhones. (a) How many students owned either a car or an iPhone (but not both)? b) How many students do not own either a car or an iPhone?

Here are all the possibilties, with numbers of each:
Cars and iPhones: 25
iPhones only: 45
Cars only: 10
neither: 100  45 25 10 = 20
a) 55 (one of either but not both)
b) 20