(2a-5)/6 = 5/12
2(2a-5) = 5
4a - 10 = 5
4a = 15

a = 15/4

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A word problem.

In order to finish a 50m dash, a runner must first pass the midpoint, 25m. To reach 25m, he must first reach the 12.5m mark, and so on. So, the runner must reach an infinite amount of midpoints in a finite amount of time. Doing so is impossible, so the runner can never even begin his race.

What's wrong here?