If p and q were parallel then the angles 1 and 2 would be supplementary, meaning they would app up to 180.
That is because, as shown in the sketch above, for two parallel intersecting lines, the red angles are equal and the blue angles likewise.
From the fact that the angles 1 and must add up to 180 degrees, we get the equation
Simplifying the above gives
adding 24 to both sides gives
finally, dividing by 24 gives
Hence, the value of x = 17 would make the lines parallel.