Anyone know the answer to this question

Greetings from Brasil....

We can conclude that:

2X > 2X - 6  → because the same expression (2X) was removed 6 units

So, now we can draw the segment (see attachment)

Looking at the figure we can say that:

     DE = 2X

     EF = 2X - 6

     DF = 3X + 5

inserting these data in DF = DE + EF:

DF = DE + EF

3X + 5 = 2X + (2X - 6)

X = 21

EF = 2X - 6 and X = 21, so

EF = 2·21 - 6

(see attachment)