The length of the basketball court is two times the width of the court with a perimeiter = 84m solve for width and length

2(l+b)=84.

l=2b.

2(2b+b)=84.

2*3b=84.

b=84/6 =14m.

l=2b=2*14

=28m.

length l=28m.

width b=14m.