Since perimeter means adding all 4 sides, you divide 86 divided by 4 equals = 21.5. Then do 21.5 + 21.5 which equals 43. And 43 + 43 = 86. So two sides are 21.5, and the other two sides are 43. So 21.5 < 43. 21.5 is the shortest sides. Hope this Helps!