Table to estimate how many pounds of dog food his dog eat in one year which of the following would be the best strategy

Let's say that the dogs eat 50 lbs of food in 50 days. That would mean they eat 50/50 = 1 pound per day. Notice I divided the weight over the number of days. The dog eats 1 pound per day, for 365 days, so in total it eats 365*1 = 365 pounds. This is just a hypothetical example. 

In general, if x is the number of days to eat 50 pounds of food, then x/50 is the expression representing the amount eaten per day (in pounds). Finally 365*(x/50) is the expression representing the total amount eaten over the whole year.

This is why the final answer is choice C