SOLUTION: If Brittany gets a 97 on her next math test, her average will be 89. However if she gets 72,her average will be 84. How many tests has Brittany already taken ?

Question 1124489: If Brittany gets a 97 on her next math test, her average will be 89. However if she gets 72,her average will be 84. How many tests has Brittany already taken ?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
If Brittany gets a 97 on her next math test, her average will be 89. However if she gets 72,her average will be 84. How many tests has Brittany already taken ?
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t = # of previous tests
A = average of previous tests
---
t*A + 97 = 89*(t+1) = 89t+89
t*A + 72 = 84*(t+1) = 84t+84
=============
t*A + 97 = 89t + 89 --> t*A = 89t - 8
t*A + 72 = 84t + 84 --> t*A = 84t + 12
-----
89t - 8 = 84t + 12
5t = 20
t = 4

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