assume that since this is a simple math problem and they only mentioned legnth and witdth,
assume a perfect rectangle
so assuming they use all the lumber
30=perimiter
perimiter=legnth around=legnth+legnth+with+width
30=2legnth+2width
undistribute
30=2(legnth+width)
divide by 2
15=legnth+width
legnth is 4 more than 2width
legnth=4+2width
subsitute
15=legnth+width
15=4+2width+width
subtract 4
11=2width+width
divide by 3
11/3=width
legnth=4+2width
legnth=4+2 times (11/3)
lefnth=4+22/3
4=12/3
legnth=12/3+22/3
legnth=34/3 feet=11 and 1/3 foot
width=11/3=3 and 2/3
legnth=11 and 1/3 foot
width=3 and 2/3 foot
