Question

ΔABC ~ ΔDEF. What is the length DF?

Answer 1

ΔABC ~ ΔDEF

that means the ratio of DF to AC = the ratio of DE to AB

$x:3.5 \\6:4$

cross multiply

$4x=6(3.5)\\4x=21\\x=\frac{21}{4}\\ x= 5.25$

so DF = 5.25 cm