Riverboat problem--System of Linear Equations

[the_slow1]

I need help, I don't even know how to do the first part, but I can solve it once its set up (any hints/suggestions are appreciated, thanks):

For this problem a)define the variables, b)write a system of linear equations, and c) solve:

A riverboat on the Mississippi Rivera travels 48 miles upstream in 4 hours. The return trip takes the riverboat only 3 hours. Find the rate of the riverboat and the rate of the current.

:?: :?: :?:
yeah im confused.

 

[arthur ohlsten]

let B be boats speed in still water
let r be rivers speed

eq1) 48/[B-r]=4 multiply both sides of = sign by by B-r
48=4B-4r

eq2) 48/[B+r]=3 multiply both sides by B+r
48=3B+3r

eq1)
48=4B-4r
4B=48 +4r
B=12+r substitute into eq2)
48=3[12+r]+3r
48=36+6r
6r=12
r=2 answer

48=4B-4r
48=4B-8
56=4B
B=14 answer

Arthur