What does x equal if the equation is 4x+15=9x

Acarnival sold tickets for $1.50 for adults and $1.00 for students. there were 54 tickets sold for a total of $70.50. write a system of equations to represent the number of adult tickets,x, and the number of student tickets,y. find the solution and explain what it means. i'll you if you me

Find dy/dx using implicit differentiation ln(20+e^xy)=y

How many $20 bills do you need to have to make $280