All of the angles when combined should equal 180 degrees.
So...
180 = 2x - 10 + 4x + 4x + 10 Combine like terms
180 = 10x -10 +10 Add
180 = 10x Divide both sides by 10 to isolate the variable
18 = x
check your work now...
2(18) - 10 = 26
4(18) = 72
4(18) + 10 = 82
82 + 72 + 26 = 180
