Given:
[tex]\text{length(l)}=2(w)+10[/tex][tex]\text{Perimeter of rectangular field=1250 yards}[/tex][tex]2(l+w)=1250[/tex][tex]\lbrack2w+10+w\rbrack=\frac{1250}{2}[/tex][tex]3w+10=625[/tex][tex]3w=625-10[/tex][tex]w=\frac{615}{3}[/tex][tex]w=205[/tex]Width of the field is 205 yards.