Chemistry and Reaction Rate Help?

I am currently doing a lab on reaction time, concentration etc. Couple things I'm confused about, though. In my notes it says reaction rate = change in concentration over time, but for this lab, my teacher has told us to simply take the inverse of the reaction time (use our calculator) and then to make a graph of concentration vs reaction rate and take the slope of the line from the graph. For that part could I not just use the formula for slope from the data I have

i.e if the first reaction rate is 2 and the next is 3 and the concentration is 45 and 3 (just throwing out random numbers) you could have 3-2/45-3 and then add all answers together?

Thanks!