we know that
the isosceles triangle has two equal sides
let's analyze two cases
first case
perimeter=22 cm
let's suppose that the known side of 6 cm is one of the two equal sides
perimeter=6+6+x
22=6+6+x-----> x=22-12----> x=10 cm
answer first case
the possible lengths of the other two sides are
6 cm
10 cm
second case
let's suppose that the known side of 6 cm is the side that is not equal
perimeter=22 cm
perimeter=6+x+x
22=6+x+x----> 2x=22-6----> 2x=16-----> x=8 cm
answer second case
the possible lengths of the other two sides are
8 cm
8 cm
