Adult tickets cost $4 more than student tickets, if you know that Robert bought 5, then you can multiply 5x4. You can then subtract those $20 from the total of $104, which would bring you to a total of $84. Then you can add the the 5 adult tickets to the 7 student tickets, which would give you a total of 12 tickets. You can then do 84/12= 7 since the cost of every ticket is now equal. Add 4 to the 7 for the cost of the adult ticket. You now have $11 as the cost of an adult ticket and $7 as the cost of a student ticket. Plug everything in to 5a + 7s = 104 if you want to verify the answers. ( a=adult, s=student)
