Respuesta :

The diagram shows that
AB = 5
AC = AB+BC = 5+2 = 7
DE = 7
DF = DE+EF = 7+x

So,
AB/AC = DE/DF
5/7 = 7/(7+x)
5(7+x) = 7*7
5(7+x) = 49
35+5x = 49
5x = 49-35
5x = 14
x = 14/5

So EF = 14/5 in fraction form
In decimal form, EF = 2.8 (since 14/5 = 2.8)