An Isosceles Triangle Has A Perimeter Of 12cm. One Of Its Side Is 5cm. What Could Be The Length Of Each Of The Other Two Sides?

The problem statement allows two possibilities.

1. The 5 cm side is one of the two equal sides. The remaining side is
  12 - 2*5 = 2
The other two sides are 5 cm and 2 cm.

2. The 5 cm side is not one of the two equal sides. The remaining sides are
  (12 - 5)/2 = 3.5
The other two sides are 3.5 cm and 3.5 cm.

Note that in either case, the remaining two sides sum to 12 - 5 = 7 cm.