James and Sarah's Lemonade Sales

James and Sarah are selling lemonade at a local festival. James sells his lemonade for $2 per cup, and he sells a total of x cups. Sarah sells her lemonade for $3 per cup, and she sells a total of y cups. Together, they earn a total of $66 from selling lemonade.

Additionally, the relationship between the number of cups they sold is given by the equation: $$x = 2y$$.

Using these equations, determine the value of y.