Respuesta :

Answer:

D

Step-by-step explanation:

Given Δ ABC is similar to Δ DEF then the ratios of corresponding sides are in proportion, that is

[tex]\frac{EF}{BC}[/tex] = [tex]\frac{DE}{AB}[/tex] , substitute values

[tex]\frac{x}{42}[/tex] = [tex]\frac{5}{30}[/tex] ( cross- multiply )

30x = 5 × 42 = 210 ( divide both sides by 30 )

x = 7

The ratio remains same

[tex]\\ \sf\dashrightarrow \dfrac{5}{x}=\dfrac{30}{42}[/tex]

[tex]\\ \sf\dashrightarrow \dfrac{5}{x}=\dfrac{15}{21}[/tex]

[tex]\\ \sf\dashrightarrow 15x=105[/tex]

[tex]\\ \sf\dashrightarrow x=7[/tex]