Given that the subway stations are 930 m apart, the train have to be accerelated for half the distance and then decerelated for the rest of the distance.
Recall that the distance travelled by an object with an initial velocity, u, for a period of time, t, at an accereration, a, is given by

But, we assume that the train accelerates from rest, thus

The maximum speed is attained at half the center of the distance between subway stations (i.e. at distance = 465 m).
Thus, maximum speed = distance / time = 465 / 23.12 = 20.11 m/s.
The possible digits could be 0, 1, 2, 3, or 4 as they would cause the entire number to round down instead of up.
Answer:
h = 60 ; x = 25
Step-by-step explanation:
You are going to want to use Pythagorean Theorem to solve these.
Pythagorean Theorem: a² + b² = c²
h² + 144² = 156²
h² + 20736 = 24336
h² = 3600
h = 60
x² + 60² = 65²
x² + 3600 = 4225
x² = 625
x = 25