Find the measure of x in circle O

x = 1/2(360 -168 - 40)

x = 76 degrees

Here is why (let O be the centre of the circle)

Consider minor arc AB

Angle ACB= half of angle AOB = 20 degrees 

{When standing on the same arc the angle at the centre will be twice the angle on the circumference.}

Consider minor arc CD

Angle CBD = half of angle COD = 84 degrees

Pink angle at E = 180-84-20 = 76 degrees.