A boat moving at 15 km/h relative to water is crossing a river 1.5 km wide. The river flows at 5.0 km/h

It will take 1.5/15 hr to get across

IT does downstream 5*1.5/15 km

For the c), draw the triangle. On side is 5km/hr, the hypotenuse is 15km/hr. Solve for the side going straight across, that is the velocity across. For the angle, SinTheta=5/15

i didn't get the answer of bob very well. can he help me more widely.
the question is

Q)A boat moving at 15 km/h relative to water is crossing a river 1.5 km wide. The river flows at 5.0 km/h
a) if the boat heads directly for the opposite shore, how long will the trip take?
b)Where will the boat arrive on the opposite shore?
c)If the boat is to reach a point directly across from the starting point , in which direction should the boat head?
d)How long will the crossing take in case c)?

use this, Vx = dx * t
then use that t and find
Vy = dy * t
x and y are x dimension n y dimension
uhh..
i'll just do it,
Vx= 15 km/hr
dx = 1.5 km
dy = 5 km/hr