Answer:
XZ = 7.5
Explanation:
A drawing is sometimes very helpful.
Start by drawing a segment with endpoints W and Z.
+--------------------------------------------+
W Z
Y is the midpoint of WZ. Draw point Y in between W and Z and the same distance from both W and Z.
+---------------------+--------------------+
W Y Z
X is the midpoint of WY. Draw X between W and Y, and the same distance to W and Y.
+----------+----------+--------------------+
W X Y Z
Because of the midpoints, we know that:
WX = XY
WY = YZ
WY = 5
WX and XY are each half of WY, so WX = XY = 5/2 = 2.5
WY = YZ = 5
XZ = XY + YZ
XZ = 2.5 + 5
XZ = 7.5