The value of x in the figure is -46.7.
What is the value of x?
The sum of angles in a triangle is 180°
Angle 1 = 48°
Angle 2 = 58°
Angle 3 = 180° - (Angle 1 + Angle 2)
= 180° - (48° + 58°)
= 180° - 106°
Angle 3 = 74°
So,
Angle 3 + (-3x - 40)° = 180° Supplementary angles
74 - 3x - 40 = 180
-3x = 180 - 74 + 40
-3x = 146
Divide both sides by -3
x = 146/-3
x = -48.7
Therefore,
(-3x - 40)°
= -3(-48.7) - 40
= 146.1 - 40
= 106.1°