I don't know what the "lowest y-intercept means" so if you can reiterate and clarify I'd appreciate it, but if you understand what you're looking for then I assume that a graph would be helpful. An online useful graphing site I like is desmos. Hope I helped.
D is distance which is 72 meters time represents seconds which is 12 so ratio is 12:72 reduce to get 1:6 time over distance would be 1/6 every second Eddie runs 6 meters so t= d/6 or 6t=d