AMC 10B 2017 Problem 4

Suppose that x and y are nonzero real numbers such that

\dfrac{3 x+y}{x-3 y}=-2

What is the value of

\dfrac{x+3 y}{3 x-y} ?

Answer Choices
A. -3
B. -1
C. 1
D. 2
E. 3