Question

A car dealership interviewed every driver who came onto their lot on Tuesday. This produced the following results: there were 68 people who owned trucks and 121 people who owned cars. If 35 people owned both a truck and a car and 15 people owned neither, how many people were interviewed?

Answer 1

n(truck)=68,n(car)=121,n(car&truck)=35,n(nothing)=15
n(total)=n(truck)+n(car)-n(car&truck)+n(nothing)
n(total)=169

Answer 2

Drawing a diagram might help. :) (see attached).

It should be easy to see that 15 people are outside the circles. (they own neither).

Cars + Trucks = 121 + 68 (big circle + small circle)
BUT
BUUUUUUT...
we must SUBTRACT 35 from that total, cuz we are "counting them twice" (that's where the circles overlap).


You should now be very near the solution.

Hope this helps!