Seeing as it is a isosceles triangle, two sides are the same length as each other.
We have been given the base, at 24cm, the two other sides must be the base taken away from the perimeter;
96-24 = 72
Then because the sides are of equal length, you can divide 72 by 2 to get the final length of one of the side lengths:
72/2 = 36
The side lengths are 36cm
The base length is 24 cm,
Hope this helps! :)