Walking trails AC and BD represent the diagonals of the parallelogram ABCD. As known the diagonals of the parallelogram bisects each other.
Then
Since DE=BE, then
y+2=3y-4,
2y=6,
y=3.
And BD = y+2+3y-4=3+2+9-4=10 miles.
Since y=3 miles and AE=CE, then
AC=2CE=2(2y-3)=2(6-3)=6 miles.
The sum of the lengths of the two trails is
AC+Bd=10+6=16 miles.
Answer: correct choice is C