The midpoint of any segment is exactly in the middle, which splits our segment into two equal halves
In our problem,
E is the midpoint
DE = x + 5
FE = 3x - 7
FE = DE
Let's solve for x
3x - 7 = x + 5
Subtract x from both sides and add 7 to both sides.
2x = 12
Divide both sides by 2
x = 6
Let's plug this into DE.
DE = x + 5 = 6 + 5 = 11