Explanation:
due to AB being parallel to XZ, we know that ABY and XZY are similar triangles.
therefore, they have the same angles, and there is one common scale factor for all side lengths from one triangle to the other.
so,
AY / XY = AB / XZ
XY = AY + AX = 7 + 6 = 13
7/13 = 14/XZ
XZ×7/13 = 14
XZ×7 = 14×13
XZ = 14×13/7 = 2×13 = 26