1)x+3x10+90=180, since the sum of all the angles of a triangle is 180 degrees. a)4x+80=180 b)4x=100 c)x=252)easy, sum of ex. anlges is 360/n(n is number of sides) a)360/12= 303)sum of in. angles of pentagon is 540 degrees, 30+70+120+165+x=540100+285+x=540385+x=540x=155
