Quick im offering 10pts and brainliest answer

The value of x is 30




Angle PJK and Angle DJB are vertical angles. They are formed when you cross PD and KB. They are opposite one another. Vertical angles are congruent, so,

(angle PJK) = (angle DJB)
3x-40 = 2x-10
3x-40-2x = 2x-10-2x ... subtract 2x from both sides
x-40 = -10
x-40+40 = -10+40 add 40 to both sides
x = 30

Side Note:
if x = 30, then angle PJK is...
angle PJK = 3x-40
angle PJK = 3*x-40
angle PJK = 3*30-40
angle PJK = 90-40
angle PJK = 50 degrees
which is also the measure of angle DJB