Question 1091781
75=0.05v^2+v; multiply by 20 both sides
1500=v^2+20v
v^2+20v-1500=0
(v+50)(v-30)=0
v=30 m/sec only positive root.
That speed is 108,000 m/3600 sec (1 hour)
That is 108 km/h and consistent with the driver's exceeding the speed limit.