Question 1005919
Well, to reach 90% after playing x more games, we write
(12 + x)/(20 + x) = .9
12 + x = 18 + .9x
.1x = 6
x = 60 games
so that her record is 72 out of 80.
Now we need to find the number of y games she can lose...
72 / (80 + y) = .75
so that
72 = 60 + .75y
12 = .75y
y = 16 games she can lose and still have a 75% winning percentage.