Hello, Melaina,

See if this makes sense (ie., is correct).

__Line D--E--F__

E is the midpoint, so DE = EF

DE = 15-3x

EF = x+ 3

Since DE = EF,

15 - 3x = x + 3

-4x = -12

x = 3

If x = 3,

DE = 15 - 3*3, 15 - 9 = 6

EF = x+ 3, so EF = 3 + 3 = 6

That makes sense, DE = EF, since E is a midpoint.

EF = 6

I hope this helps,

Bob