Answer:
x = 35
Explanation:
angles in a triangle add up to 180.
x + 11 + 3x + 1 + x - 7 = 180
combine like terms
5x + 5 = 180
subtract 5 from both sides of the equation
5x + 5 - 5 = 180 - 5
5x = 180 - 5
5x = 175
divide both sides of the equation by 5
5x/5 = 175/5
x = 175/5
x = 35