A local charity organization is organizing a fundraising event and has established a system of equations to model their revenues and expenses. The equations are:

$$3x + 2y = 60$$

$$4x - y = 10$$

Here, x represents the number of premium tickets sold, and y represents the number of regular tickets sold. Determine the value of y in terms of x and subsequently find the exact number of regular tickets sold when the revenue reaches $40. Provide your answer as an integer.