To get x the lines on the sides of the triangle mean the three sides are congruent. The angle across from that side are equal. So that makes all three angles equal. In every angle it’s 9x-3 so you add that together and you get 27x-9. All triangles equal 180 so do 27x-9=180 add 9 to both sides, +9 +9 and you get 189 27x=189 Divide by 27
