CCSS IP Math II 5.3.2 Example 2

Explain why [math]\bigtriangleup{ABC}\sim\bigtriangleup{DEF}[/math], and then find the length of [math]\overline{DF}[/math].

[list=1] [*]Show that the triangles are similar. [*]Find the length of [math]\overline{DF}[/math]. [/list]