Geometry HELP! segments?? length

Given X is the midpoint of (segment) YZ. Given (segment) XY = 6x+4 and (segment) YZ=40, find the value of x.


please help and explain work!

Y------------------X---------------Z
6x+4
40

If x is the midpiont of YZ then its true that 2 times the length of YX = YZ right?...

2(6x+4) = 40
6x + 4 = 20
6x = 16
x = 16/6 = 8/3