Respuesta :

width=x
length= 3x+4
perimeter= 56

To find the perimeter you have to add all the sides
So it will look like this:

x+(3x+4)+x+(3x+4)=56
8x+8=56
8x=56-8
8x=48
x=48/8
x=6

The width is 6 m long
calculate length 3(6) + 4
The length is 22 m long