Try finding the constraints in the given problem
perimeter of rink is 570 ft ( i )
let x be the width of the field
so x+115 will be the length.
once you get this, rest is simple.
Now from Perimeter of the rink will be (as the rink is rectangular)
= 2x + 2(x+115)
= 4x + 230 ( ii )
from ( i ) and ( ii )
4x + 230 = 570
4x = 340
x = 85
width = x = 85, length = x+115 = 200
Now you know both the dimensions
