<h3>Sample space = {a,b,c,d,e,f}</h3><h3>Event space = {a,c}</h3>
We simply list all of the letters mentioned as they are the possible outcomes. We can only pick one item from the sample space. The event space is the set of outcomes where we want to happen (picking either an 'a' or 'c').
Let
be the speed of train A, and let's set the origin in the initial position of train A. The equations of motion are

where
are the positions of trains A and B respectively, and t is the time in hours.
The two trains meet if and only if
, and we know that this happens after two hours, i.e. at 

Solving this equation for v we have

So, train A is travelling at 105 km/h. This implies that train B travels at

It was reduced because as you can see on the scale the actual picture has larger spaces between the numbers.
Are you trying to find x? send the whole question xoxo