X/y = 2 so x = 2y
z/x = 4 so z = 4x but x = 2y so z = 4(2y) = 8y
now you have
x = 2y, z = 8y
x + y + z 2y + y + 8y 11y 11
------------ = -----------------------= ------------- = ----------- = 5 1/2
x 2y 2y 2
answer
C. 5 1/2
Well... looking at proportions, we're being asked
