Answer:
A
Explanation:
AC = 5
DF = 15
5 x 3 = 15
BC = 3
EF = 9
3 x 3 = 9
Do you see the pattern? So as you can see the difference between Triangle ABC and DEF is the multiply/divide 3 so if you want to find DE then you should set it up as:
=
and to check if its right if you solve it you get
=
and as you see
and
are literally the same thing just you need to simplify