Answer: Boat cost $ 3200 
Trailer cost $ 800
Step-by-step explanation: From the statement , the coat of Trailer (t) = 1/4 of the coat of the boat ( b)
i.e t = 1/4b
multiply through by 4
4t = b 
both cost 4,000
i.e t + b = 4000
recall: b = 4t
therefore 
t + 4t = 4000
 5t = 4000
 t = 4000/5
 t = 800
 b = 4000 - 800
 b = 3200