Question

what does the attendance need to be on saturday to have an average attendance for the week of 30 people per day?
sunday monday tuesday wednesday thursday friday saturday
day
attendance 54 29 22 28 12 15 ?

Explanation:

Step1: Calculate total expected attendance

The week has 7 days and the average attendance per day is 30 people. So the total expected attendance for the week is $30\times7 = 210$ people.

Step2: Calculate sum of known - day attendances

Add the attendances of Monday - Friday: $54 + 29+22 + 28+12+15=160$ people.

Step3: Calculate Saturday's attendance

Subtract the sum of known - day attendances from the total expected attendance. Let the Saturday's attendance be $x$. Then $x=210 - 160=50$ people.

Answer:

50