Question 742014
See carefully how the length of one rectangle is given and the width of the other similar rectangle is given.  

First rectangle:  {{{2*9+2*w=30}}}
{{{9+w=15}}}
{{{w=15-9=6}}}
Dimensions: Length 9, Width 6.


Similar rectangle is of width 3, therefore, since distance dimensions are in proportion 3/6=1/2, the length is {{{9/2=highlight(4&1/2)}}}.
Dimensions: length {{{4&1/2}}}, width 3.


Perimeter of this similar rectangle is {{{2*4.5+2*3=highlight(15)}}}. Done.