Help me out
Length = m

[tex]perimeter = a + b + c[/tex]
[tex]perimeter = 4 + 3 + c[/tex]
//
[tex] {a}^{2} + {b}^{2} = {c}^{2} [/tex]
[tex] {4}^{2} + {3}^{2} = {25}^{2} [/tex]
[tex] \sqrt{25} = 5[/tex]
[tex]c = 5 \: meters[/tex]
//
[tex]perimeter = 4 + 3 + 5[/tex]
[tex]perimeter = 12 \: meters[/tex]
//
[tex]the \: length \: of \: the \: fencing \: is\: 12 \: meters[/tex]