Help me melody

2 out of 5 students voted for John. The other students voted for Tommy. If 9 students voted for Tommy, how many students voted in all?

In every group  of 5,  2 voted for John and 3 voted for Tommy

So

2/3  of Tommy's vote  = Jonh's vote

(2/3) (9)  =   6  voted for John

9 +  6   =    15   voted