so easy this is very easy hmmm lets say y is the total cost and x is the day briy briy ummm so flat rental fee of 55 once so thats our b and 8.50 each day wow money lovers..... I could have bought a guitar pick (btw I like playing guitar) anyways x is day so 8.5x oh y is given thought ur going to graph this so simple so its 123=8.5x+55 and solve this thing and x is 8 days wow 4 this price u could get a cheap bike dont u rent that bike!!!