Because the 2 sides of the triangle are the same, they are both 21, the two bottom angles would also be the same.
The 3 inside angles of a triangle must equal 180 degrees.
The top angle is given as 38, so the remaining two angles must equal 180 - 38 = 142 degrees.
Since the 2 bottom angles would be the same, divide 142 by 2 to get x.
X = 142 / 2 = 71 degrees.
