Susan runs y yards in 9 seconds which means her rate over that particular distance is: r = y/9
We're told to look for how long it will take her to run x yards at the same rate
t = d/r
t = x/r
t = x/(y/9)
t = 9x/y
This gives us the time in seconds but we need to multiply by 60 (seconds) to get the time in minutes.
t = 9x/60y
I had a bit of trouble conceptualizing this problem at first, specifically why we would find the time of the new distance (in minutes) by dividing by the old rate. Well, I guess it was a silly problem to be caught up on. All we want to know is how long (t) it will take for x yards to be covered at the same rate we determined to be (y/9) Then, we just had to multiply by 60 seconds to get y in terms of minutes. I guess the final answer tripped me up because of the way it multiplied out (in other words, if t = d/r then why is d here equal to 9 seconds*x distance.) I'm not sure what I can do to help me better understand these kinds of problems. ANSWER: b.) 9x/60yP.S. Bunuel, I believe you got the correct answer (it's the same one I got) but you marked down the incorrect answer choice.