Yeah, it's just a matter of finding a formula for what you're looking for and plugging in the unknowns.
Like number 1, it asks for the rate of change of the distance between them.
The distance D between them is
D(t) = Sqrt(x(t)^2+y(t)^2)
where x(t) is the distance between them in x and y(t) is the distance between them in y. We'll call +/- x East/West respectively and +/- y North/South respectively, assume 2 PM is t=0, and t is in hours.
The rate of change of the distance between them is
d/dt(D) = dD/dt = (2x(t)x'(t)+2y(t)y'(t))/(2sqrt(x(t)^2+y(t)^2))
(so ugly in ASCII form, I know)
( d/dt(sqrt(u)) = 1/2 * 1/sqrt(u) * du/dt = du/dt / (2sqrt(u)) and our u(t) = x(t)^2+y(t)^2 thus u'(t) = 2x(t)x'(t)+2y(t)y'(t) )
So then all you need to know are the unknowns of dD/dt: x, y, x', y', and t which is 4.
x(t) = 150-35t km
y(t) = 25t km
x'(t) = -35 km/h
y'(t) = 25 km/h
(Really x' and y' are given and we integrate to get x and y, but in this case it's so mentally intuitive we have no need to show it explicitly)
Plug everything in for dD/dt|t=4 and you get the answer. I hope I did this right.
Same procedure for the others with different functions.