In the city of San Durango, 40 people own cats, dogs, or rabbits. If 20 people owned cats, 30 owned dogs, 10 owned rabbits, and 10 owned exactly two of the three types of pet, how many people owned all three? Choose the correct answer.
A) 5
B) 7
C) 9
D) 11
E) 13
Total = C + D + R - (CD + DR + CR) - 2CDR   40 = 20 + 30 + 10 - (10) - 2x   x = 5   So, answer will be 5
<result>A</result>
In the city of San Durango, 40 people own cats, dogs, or rabbits. If 20 people owned cats, 30 owned dogs, 10 owned rabbits, and 10 owned exactly two of the three types of pet, how many people owned all three?