Let's calculate the mean of the 5 lunches in the first week. We calculate the mean by adding all the numbers up and dividing by how many numbers there are. So we have:

So this is the mean of the 5 lunches in the first week. We are told that in the second week he spent $3 more on his 5 lunches, let's calculate the mean of the second week:

This is the mean for the second week. Subtract it from the mean in the first week to find the increase:
