Firstly you have to reduce the 4 variables to a double system of equation with only 2 variables.
Let's say, first we have to eliminate Z:
Take 1st & 3rd equation & multiply each term of the 1st by (- 1). One done you add up the 1st & the 3rd & you will get:
5W - 4x + 2y = - 18
Follow the same methodology to find another equation without z. Once done you will have a system of 2 equation with 2 variable easy to solve,
At the end you will find:
w = -3
x = -2
y = -1
z = 3
It would be B, 6.5 inches
Mid-segment and bottom side of the triangle is always parallel to each other, and parallel lines must have same slopes, so if their slopes are equal, then MN would be mid-segment of side AB in Triangle ABC
Hope this helps!