You have x + 4y = 6 and x = 2y, and you want to compare x and y. Let’s start by finding y. Substitute 2y for x in the first equation and get 2y + 4y = 6 or 6y = 6. Divide both sides by 6 and get y = 1. If y = 1 and x = 2y, as the second equation states, x must equal 2. Because 2 is greater than 1, Quantity A is greater.