This is an isosceles triangle because the picture shows it has two equal sides. Isosceles triangles have two equal angles.
The sum of all the angles of a triangle = 180º.
We can use this equation to solve for x:
2x + 54 = 180.
- 54 -54 Subtract 54 from both sides.
2x = 126
/ 2 /2 Divide 2 from both sides to isolate x.
x = 63º
Let's check! 63 + 63 + 54 = 180? YUP!