Answer:
Perimeter formula of a rectangle:
[tex]perimeter = 2(length + width)[/tex]
perimeter » 26 cm
width » 4 cm
let the length be l :
[tex]26 = 2(l + 4)[/tex]
divide all sides by 2:
[tex] \frac{26}{2} = \frac{2(l + 4)}{2} \\ \\ 13 = l + 4[/tex]
subtract 4 from either sides:
[tex]13 - 4 = (l + 4) - 4 \\ 9 = l \\ \\ { \boxed{ \boxed{length = 9 \: \: centimeters}}}[/tex]