A tennis team has won 15 out of 20 matches they have played this season. How many more will they have to win in a row to raise their winning percentage to 90%

I'm not sure if you were looking for this specific answer but if they wanted 90% they would've had to win 18/20 games

OR

If they play they will have to play 30 more games and win ALL of them to raise it.

Step-by-step explanation:

You see, 15/20 = 75% ... 75% = 75/100. So, (15 + t) / (20 + t) = 90% ... 90% = 90/100. Solve for (t).

(15 + t) / (20 + t) = 90/100

90 (20 + t) = 100 (15 + t)

1800 + 90t = 1500 + 100t

10t = 300

t = 30 matches

The team would have to win 30 more matches in a row (that's 45 out of 50 matches).