We have to use proportions to solve this question.
According to the given information, the perimeter of Figure A is to the sidelength of that figure as the perimeter of Figure B is to the sidelength of that figure:
[tex]\begin{gathered} \frac{48}{18}=\frac{80}{x} \\ x=\frac{80\cdot18}{48} \\ x=30 \end{gathered}[/tex]The corresponding sidelength of Figure B is 30.
