A playlist initially contains 45 rock tracks and 15 jazz tracks. Then $x$ rock tracks are deleted

Question

A playlist initially contains 45 rock tracks and 15 jazz tracks. Then $x$ rock tracks are deleted and $x-3$ jazz tracks are added. Every remaining track is equally likely to be played next. The probability that the next track is jazz is $\frac13$. Find $x$.

Accepted Answer

$x=7$.

Probability and changing counts

Probability and changing counts

Solution:

Solution locked