The midpoint divided a segment into two congruent lengths/segments.
So, QM = MR.
Set up the equation.
16 + x = 2(x+ 2)
16 + x = 2x + 4
12 + x = 2x
12 = x
Now, that you have the value of x, substitute it for the two equations.
QM = 16 + x
QM = 16 + 12
QM = 28
MR = 2(12+ 2)
MR = 2(14)
MR = 28
Find the whole length by of the line by adding the two segments. 28 × 2 = 56.
QR = 56