Since triangle XYZ is dilated by a scale factor 3 to form the triangle TUV
That means each side of triangle TUV is 3 times the corresponding side in triangle XYZ
TU = 3(XY)
UV = 3(YZ)
Since UV = 39
39 = 3(YZ)
Divide both sides by 3
39/3 = YZ
13 = YZ
The length of YZ is 13
The answer is A