You can tell that the triangle is isosceles because of the two congruent sides. In an isosceles triangle, when two sides are congruent, their corresponding angles also are. So by that, you can determine A=C. You then set up the equations equal to each other.
5x+16 = 2x +43 3x+16 = 43 3x = 37 x=9
Then, plug x in.
5(9) + 16 = 61
and
2(9)+43 = 61
After that, you can add up 61 and 61, which equals 122. All triangles add up to 180, so you would do 180-122.
