How do you set this up?

Question

Solve the system using substitution:
A boat travels 18 miles downstream in 1.5 hrs. It then takes the boat 3 hrs. to travel upstream the same distance. Find the speed of the boat in still water and the speed of the current.

Thanks you!!!

Answer 1

if the boat's speed is b, and the current is c,

distance = time * speed

1.5(b+c) = 18
3(b-c) = 18

now go solve 'em.

Answer 2

Thank you for your help!