How many cans of dog food must Sam buy for his 3 dogs if each dog eats 2 cans per day? Sam only shops once a week.

To find the answer you can set up an equation like this: 3 (x) (d)

x would stand for number of cans each dog eats, while d stands for the number of days in a week. 3 (2) (7) = 42 Sam would have to purchase 42 cans of dog food each week.