Answer:
a
Step-by-step explanation:
If a line is parallel to a side of a triangle and it intersects the other 2 sides then it divides those sides proportionally. that is
[tex]\frac{A'B'}{AB}[/tex] = [tex]\frac{A'C}{AC}[/tex] , substitute values
[tex]\frac{A'B'}{12}[/tex] = [tex]\frac{4}{6}[/tex] ( cross- multiply )
6 A'B' = 48 ( divide both sides by 6 )
A'B' = 8
