how loing will it take a falling rock, accelerating at 9.8 m/s 2 ​, to reach 112 m/s, if it startsfrom rest?

Using

Vf  = Vi  -9.8t       where Vi  is the initial velocity  [ = 0]   and Vf is the final velocity = -112m/s

So we have

-112 = -9.8t         divide both sides by -9.8

-112 / -9.8   = t  ≈  11.429 s