For some reason, this is one of only two questions I'm stumped on right now.

I've calculated the distance @ 21/10. But when I follow the examples in Stewart Calculus ed:7 I can't work out how to calculate the velocity.

Time = 7, distance = 21/10. I'm not even close to the answer, or even sure how I'm supposed to go about the problem.

Not asking for it to be done, just a step in the right direction.