X/y + 9 = n Solve for y

Last saturday, the museum box office sold 281 tickets for a total of $3,954. adults ticket cost $15, and students ticket cost $12. how many of each kind of tickets were sold?

Mary used 1/7 of a spool of ribbon to complete 4 projects. she used the same amount of ribbon on each project. how much ribbon did she use on each project?

Given f(x)= 9x+1 and g(x)=x^3, choose the expression (f*g)(x)