Answer:
Step-by-step explanation:
That line that separates the triangle vertically is an angle bisector. That creates a ratio between the resulting 2 triangles:
[tex]\frac{6}{3x-12} =\frac{14}{21}[/tex] and cross multiply:
14(3x - 12) = 21(6) and
42x - 168 = 126 and
42x = 294 and
x = 7
