In order to determine the value of x, consider that one of the interior angles of the triangle is given by:
180 - (4x - 18)
= 180 - 4x + 18
= 198 - 4x
Next, consider that the sum of the interioir angles of a triangle is equal to 180:
(2x + 6) + 36 + (198 - 4x)
= 2x + 6 + 36 + 198 - 4x
= -2x + 240
this is equal to 180:
-2x + 240 = 180
-2x = 180 - 240
-2x = -60
x = 60/2
x = 30
Hence, the value of x is x = 30
