PLEASE HELP .!!! ILL GIVE BRAINLIEST.. *EXRTA POINTS* .. DONT SKIP :(( ! 
ILL GIVE 40 POINTS . 
                                             
                                          
                                          
                                        
											 
											Answer:
7
Step-by-step explanation:
it says that there is 1/3 of tuba players than trumpet players so divide 21 by 3 and you get 7 which is the answer
hope I helped ;)