In case of Nina:
slope of graph = speed = 48-32/6-4 = 16/2 =8
y-32 =8(x-4)
y-32=8x-32
y=8x
d=8t
at x= 0 i.e at t= 0
d= 0m
In case of Ryan:
slope =speed = 47.5-35=6-4 = 12.5/2 =6.25
y-35=6.25(x-4)
y-35=6.25x-25
y=6.25x+10
d=6.25t+10
at t = 0, d= 10m
RYAN had a head start of 10 m