Answer :
Here as the Pentagon is regular so it's all sides will be of equal length . And if we assume It's each side be s , then it's perimeter is going to be (s+s+s+s+s) = 5s.And as here , each side is increased by 8 inches and then it's perimeter is 65 inches , so we got that it's side after increament is (s+8) inches and original length is s inches . And if it's each side is (s+8) inches , so it's perimeter will be 5(s+8) and as it's equal to 65 inches . So , 5(s+8) = 65
[tex]{:\implies \quad \sf 5(s+8)=65}[/tex]
[tex]{:\implies \quad \sf 5s+5\times 8=65}[/tex]
[tex]{:\implies \quad \sf 5s+40=65}[/tex]
[tex]{:\implies \quad \sf 5s=65-40}[/tex]
[tex]{:\implies \quad \sf 5s=25}[/tex]
[tex]{:\implies \quad \sf s=\dfrac{25}{5}=5}[/tex]
[tex]{:\implies \quad \bf \therefore \quad \underline{\underline{s=5\:\: Inches}}}[/tex]
As we assumed the original side to be s .
Hence, the original side's length 5 inches