NSolve[{Quantity[11.2, ("Radians")/("Seconds")] == a t,
  t == Quantity[2.92, "Seconds"], d == .5 a t^2}, {a, t, d}]

{{t -> Quantity[2.92, "Seconds"],
  a -> Quantity[3.83562, 1/("Seconds")^2], d -> 16.352}}