Ninety passengers rode in a train from City A to City B. Tickets for regular coach seats cost $121. Tickets for sleeper cars seats cost $285. The receipts for the trip totaled $19,418. How many passengers purchased each type of ticket?
r = # regular revenue from = 121r
s = #sleeper = (90-r) revenue from = 285 (90-r) summed , these = 19418
121 r + 285 (90-r) = 19418 solve for 'r' the # regular then # sleeper = 90-r