The correct answer is - 50.
In order for the art show to have an average of 30 people per day for the week we first need to find out what would be the sum of all the people if there were 30 people per day. Since there's seven days in a week we need to multiply the days in the week with 30:
7 x 30 = 210
So we should have 210 people for the whole week in order to have an average of 30 people per day. Now we need to see how much people have attended in all days apart from Saturday by gathering the numbers of all other days:
54 + 29 + 22 + 28 + 12 + 15 = 160
So if in the six days we have information about 160 people attended the art show, we only need to take out those people from the number required for them to be 30 per day:
210 - 160 = 50
We come to a result that 50 people should attend in Saturday in order for the art show to have an average of 30 people per day.
