physics
posted by john .
Solve for v1.
O.500km/v1+3.50km/2v1=0.250h

(2.25 km)/v1 = 0.25 h
v1 = 9 km/h
h would have to have dimensions of time for this to make any sense. I assume the "h" means hours in this case 
How did you get 2.25/v1?

I did the algebra, combining the two terms on the left.
3.50km/(2v1) = 1.75km/v1
Add 0.50km/v1 to that 
Thanks I don't know I could forget that. Is this like algebra?

Yes. You need to do some algebra to get the answer. You don't need any physics.