Respuesta :

If both triangles are similar then ratio of sides will be same.

[tex]\\ \sf\longmapsto \dfrac{12}{14}=\dfrac{y}{21}[/tex]

[tex]\\ \sf\longmapsto 12(21)=14y[/tex]

[tex]\\ \sf\longmapsto 14y=252[/tex]

[tex]\\ \sf\longmapsto y=\dfrac{252}{14}[/tex]

[tex]\\ \sf\longmapsto y=18[/tex]

Answer:

y = 18

Step-by-step explanation:

Since the triangles are similar, the corresponding sides are in proportion, that is

[tex]\frac{BC}{EF}[/tex] = [tex]\frac{AC}{DF}[/tex] , substitute values

[tex]\frac{y}{12}[/tex] = [tex]\frac{21}{14}[/tex] ( cross- multiply )

14y = 252 ( divide both sides by 14 )

y = 18

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