~3.6 mph VHilary - 2 mph Vriver = ~1.6 mph; 3.4 / 1.6 = 2.1 ~= 2:07
~3.6 mph VHilary + 2 mph Vriver = ~5.6 mph, 3.4 / 5.6 = .62 ~= 0:37
I love that you actually did it! I did it on paper and got the same. I guess we both know our algebra.
I was too lazy to do the algebra. I just cheated and incremented in Excel. This is also why I didn't learn substitution when they started with nickels and dimes as examples.
It was my understanding there would be no math involved...