2. (33) A bag contains 5 red marbles and 4 blue marbles. Find the probability of
drawing a blue marble, keeping it, and
drawing another blue marble. Write the
probability as a fraction in simplest form.

> Last year the ratio of the number of middle school students
> to the number of high school students was 1:8.
1/9 x + 8/9 x = makeup of middle and high school students

> this year the ratio ... changed to 2:7
2/9 x + 7/9 x = x (again)

> there are 18 middle school students in the band this year
2/9 x = 18
2x = 9 * 18 → x = 81

Total = 81 in band ...
Last year:
1/9 and 8/9 = 9 and 72
This year
2/9 and 7/9 = 18 and 63

And from there you can figure out the changes:
+9 for middle school (which is increase from 1/9 to 2/9)
--9 for high school (which is decrease from 8/9 to 7/9)