x=13 since the triangle adds up to 180, you know one side is 90 degrees and the other two angles are equal to each other because the opposite sides are equal to each other. the two angles must add up to 90 degrees so you divide by 2 and you get 45 degrees for each angle E and G and you set 3x+6=45. you subtract both sides by 6 and then you have 3x=39 and now divide both sides by 3 and x=13.