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
The correct answer is -3.6. Hope this helps!!
The equation that would represent the new area N of the floor of the cage would be
N=w2+4w which would be a
