The angles inside a triangle add up to 180°
The 3rd angle is supplementary to (6x+1)°
Supplementary means they make a straight line (i.e 180°)
1st angle = 79°
2nd angle = (2x+10)°
3rd angle = 180° - (6x+1)°
180 = 79 + (2x+10) + 180 - (6x+1)
180 = 79 + 2x + 10 + 180 - 6x - 1
combine like terms
180 - 180 - 79 - 10 + 1 = 2x - 6x
-88 = -4x
-88/-4 = x
22 = x
