SOLUTION: Mary had an average score of 78 points over x number of tests. How many marks must she score for her next test so that she can get an average of 80 points?

Algebra ->  Average -> SOLUTION: Mary had an average score of 78 points over x number of tests. How many marks must she score for her next test so that she can get an average of 80 points?      Log On


   

Question 703212: Mary had an average score of 78 points over x number of tests. How many marks must she score for her next test so that she can get an average of 80 points?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Mary had an average score of 78 points over x number of tests.
How many marks must she score for her next test so that she can get an average of 80 points?
:
Let t = the score required to raise the av to 80
:
%28%2878x+%2B+t%29%29%2F%28%28x%2B1%29%29 = 80
multiply both sides by (x+1)
78x + t = 80(x+1)
78x + t = 80x + 80
t = 80x - 78x + 80
t = 2x + 80, is the scored required to get an 80 av