posted by kayla .
A student has scores of 72, 78, and 87 on three government exams. What score does she need on a fourth exam to give her an average of 80 or better?
add up the total points. To average 80 on 4 exams, she need 4*80 = 320 points.
So, add up her scores so far; how many more does she need to get to 320?