Step-by-step explanation
By definition, the mean value of a set of data with n elements x₁, ..., xₙ, is given by:

We see that the numerator S is the sum of all the numbers in the set.
We know that the ice cream shop sold the following number of ice creams during the week: 54, 45, 33, 39, 48, 40, 41. The sum of these numbers is:

The mean value for this quantity is:

But for a mean value m' = 45 and n' = 7, we must have a sum:

To have a mean value of 45, the shop must sell:

ice creams more.
Answer
D. 15