От Тайынши до Кызылжара поезд шел 14 часов. Обратный путь этот
поезд прошел со скоростью на 40 км в час большей и поэтому прошел
весь путь на 4 часа быстрее. Найдите расстояние от Тайынши до
Кызылжара.

Explanation:

Translated to English the question is that a train went in 14 hours from Tayinshi to Kyzylzhar. On the way back, the train passed at a speed of 40 km per hour more and therefore passed 4 hours faster all the way. Find the distance from Taiynshi to Kyzylzhar.

The equation for the distance d covered at constant speed v, in time t, is:

For the time of 14 hours, you can write:

For the way back, the time is 4 hours less, 10 hours, and the speed 40km/h more, v + 40km/h, then the equation becomes:

Equal the two equations:

Solve:

Replace v = 100km/h in the first equation:

b.

explanation:

just because.

well, the b sentence is the only one that has sense.