Triangle tuv was dilated to create triangle t'u'v' using point a as the center of dilation. what is the scale factor of the dilation?

The
the complement of the question is as follow
What is the scale factor of the dilation?

when we look at the image, 

UV and U'V' are parallels, and (A, U V)  and (A, U' V') are aligned points
so we can apply thales theorem
AV/AV' = AU / AU'= VU /V'U'= 3.2+4.8/ 3.2= 8/3.2

so VU / V'U'= 8/3.2, the image is formed by a reduction  

    VU  = 8/3.2  V'U', so k=8/3.2 
the scale factor of the dilation is k=8/3.2 

The answer is c. 7 (i think) i’m almost sure though