An isosceles triangle has two sides of equal length. Let the two unknown sides have measurement x.
perimeter= AB+BC+CA
20= x+ x+ 8
20= 2x + 8
2x = 20-8
2x= 12
x=6
So measure of side BC is 6.
perimeter= AB+BC+CA
20= x+ x+ 8
20= 2x + 8
2x = 20-8
2x= 12
x=6
So measure of side BC is 6.