Question 1199701
5n, number of pupils in class
2n, how many wear glasses
3n, how many do not wear glasses


The change - five pupils who did not wear glasses now do wear glasses.
5n pupils in class
2n+5 who now do wear glasses
3n-5 who now do not wear them


The question:  what is the ratio of pupils who wear glasses to those who do not 
if 5 of the pupils who did not wear glasses now do?


That ratio is  {{{(2n+5)/(3n-5)}}}.  



maybe about the most or best that can be done.
The class must be of at least 10 students for the description to be meaningful.