[tex]\qquad\qquad\huge\underline{{\sf Answer}}♨[/tex]
Let's solve ~
Assume width of rectangle be " x ", length = 3×width + 8 = 3x + 8 ~
Now, Perimeter of rectangle is :
[tex]\qquad \sf \dashrightarrow \:2(l + w) = 56[/tex]
[tex]\qquad \sf \dashrightarrow \:2(3x + 8 + x) = 56[/tex]
[tex]\qquad \sf \dashrightarrow \:2(4x + 8) = 56[/tex]
[tex]\qquad \sf \dashrightarrow \:4x + 8 = 56 \div 2[/tex]
[tex]\qquad \sf \dashrightarrow \:4x + 8 = 28[/tex]
[tex]\qquad \sf \dashrightarrow \:4x = 28 - 8[/tex]
[tex]\qquad \sf \dashrightarrow \:x = 20\div 4[/tex]
[tex]\qquad \sf \dashrightarrow \:x =5 \: cm[/tex]
Hence, width = x = 5 cm
[tex]\qquad \sf \dashrightarrow \:l = 3w + 8[/tex]
[tex]\qquad \sf \dashrightarrow \:l = 3(5)+ 8[/tex]
[tex]\qquad \sf \dashrightarrow \:l = 15+ 8[/tex]
[tex]\qquad \sf \dashrightarrow \:l =23 \:cm[/tex]
And, length = 26 cm