Length is 48 ft
The perimeter of a rectangle is equal to the sum of all side’s.
2(lengths)+2(widths)= perimeter
Length=3x+4
Now given the perimeter of 140
3(3x+4)+3(x)=140
9x+12+3x=140
12x+12=140
12x=128
X= 10.7
10.7 is the width
Length=3x+4
Length =3(10.6)+4
Length=31.8+4
Length=35.8
Answer = 35.8
This can only be answered if you were given a perimeter.