So remember that the perimeter is the sum of all the sides. Using this info, we can solve each of the problems as such:
7.
[tex]x+x+x+x=32\\4x=32\\\boxed{x=8}[/tex]
8.
[tex]k+k+7+k+11=45\\3k+18=45\\3k=27\\\boxed{k=9}[/tex]
9.
[tex]y+5y+6y-3=57\\12y-3=57\\12y=60\\\boxed{y=5}[/tex]
