Answer: 187.30
explanation for answer:
Let the measure of the unknown angle is x °
Supplementary angles sum up to 180°. So the supplementary angle of x° will be (180 - x)°
According to the given data, measure of x is 40° less than 3 times the measure of its supplementary angle (180 - x). So we can set up the equation for this scenario as:

So the degree measure of the required angle is 125°.
6a^2 - 2 -6 a -5a = 0
6a^2 -11 a - 2 = 0
a = 2 , a= -1/6