The measures of the angles of triangle ABC add up to 180 degrees:

(x-15) + (x/2 +y) + (y+15) = 180

(x + x/2) + (y + y) + (-15 + 15) = 180 *Like terms grouped together*

3x/2 + 2y = 180

We also know that ∠DAB = x + (x - 15) + (x/2 + y) and that ∠DAB is a straight angle, so:

x + (x - 15) + (x/2 + y) = 180

5x/2 + y -15 = 180

5x/2 + y = 195

We now have a system of equations we can use to solve for x and y:

5x/2 + y = 195

3x/2 + 2y = 180

There are multiple ways to solve a system of equations; I chose to multiply the top equation by -2 and use elimination:

-5x - 2y = -390

3x/2 + 2y = 180

-7x/2 = -210

Multiply both sides by -2/7 and we get:

**x = 60**

You can plug that in to the equation of your choice and find that **y = 45**.

Just to check, we can find that the angles of the triangle are 45, 75 and 60, which add to 180.