All you have to do is add up the side lengths we already know then subtract by the perimeter.
60.3 is the side lengths all together that we know
82-60.3=21.7
Hope this helped!!
there is no B i see A and -5A unless its for -5A??
No. Just because the angles are all less than 90 degrees, that doesn't tell us anything about the sides. The sides are all congruent ONLY if all 3 angles are 60 degrees each. If the angles all have different sizes, then so do the sides.