A washer and a dryer cost $1000 combined. The cost of the washer is three times the cost of the dryer. What is the cost of the dryer?

Let X be the cost of the dryer.

So the cost of the washer is 3*X.
Thus, X + 3*X = $1000.
Thus, 4*X = $1000.
Thus, X = $<<1000/4=250>>250. Answer: \boxed{250}.