ASAP answer please!!!!!!!!!!!

because the triangle above is an isosceles triangle, then both angles are of the same value.
and one thing you should know, the angle above shows the straight angle.
so the sum of all angles is 180°
can be written like this :
(5x+13)°+(3x+7)°=180°
5x + 13 + 3x + 7 = 180
8x + 20 = 180
8x = 180 - 20
8x = 160
x = 20
(*the third choice is correct)