If jack was traveling at 100 miles in 2 hours what was his velocity in miles per second

We don't know anything about the direction Jack was traveling, so we can't determine his velocity.  The best we can do is work with his speed.

Speed = (distance covered) / (time to cover the distance)

Speed = (100 miles) / (2 hours)

Speed = 50 miles/hour

The question has specified a different unit, so we'll need to convert the unit of our answer.  

Let's multiply the answer by (1 hour / 3600 seconds).  The numerator and denominator of this fraction are both the same quantity, so the value of the fraction is ' 1 ', and multiplying the answer by it won't change the answer in any way except the unit.

Speed = (50 mi / hr) x (1 hr / 3600 sec)

Speed = (50mi · 1hr)  /  (hr · 3600sec)

Speed = 50 mi / 3600 sec

Speed = 0.01389 mi/sec

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.