Take into account this is an isosceles triangle, then, there are two angles with measures 72°.
Then, the value of x is the result of subtracting two times 72 to 180 (becasue the sum of the interior angles of any triangle is 180) just as follow:
x = 180 - 2(72)
x = 180 - 144
x = 36
Hence, the value of x is 36°
