2015 AMC 10A Problem 6

Let $x$ and $y$ be the two numbers. Then we have that $$x + y = 5(x - y).$$ Note that we are assuming $x \gt y.$ This gives us $$x + y = 5x - 5y$$$$6y = 4x.$$ Dividing through yields $$\dfrac{x}{y} = \dfrac{6}{4} = \dfrac{3}{2}.$$ Thus, B is the correct answer.