12. In a recent survey, 63 persons said they either had a dog or cat as a pet. If 41 said they had a dog, and 36 said they had a cat, how many persons had a dog and cat?

14. The SMPT group at UB sells past final exams packages (small and large) for $2 and $3 respectively. This morning they sold 8 more small packages than large packages and made $156.

How many large packages were sold?

19. At $14.25, the demand (customers) for UB-shirts is 400. When the price increases to $16.55 the demand drops to 350. What is the demand when the price is $15?