Answer:
see explanation
Step-by-step explanation:
Since the triangles are similar
(a)
The corresponding angles are congruent , that is
∠ A = ∠ D , ∠ B = ∠ E , ∠ C = ∠ F
(b)
The ratios of corresponding sides are equal, that is
[tex]\frac{AC}{DF}[/tex] = [tex]\frac{BC}{EF}[/tex] , substitute values
[tex]\frac{?}{21}[/tex] = [tex]\frac{8}{24}[/tex] ( cross- multiply )
24 ? = 168 ( divide both sides by 24 )
? = 7
