Since this is an equilateral triangle, all 3 angles are equal, and all the sides are equal. 6x - 3 = 3x + 6 6x -3x = 6 +3 3x = 9 x = 3 we can check it by plugging 3 into each side for x: 6(3)-3 = 18-3 = 15 3(3)+6 = 9+6 = 15 5(3) = 15 So yes, the x = 3
