X+0.5X= 15 or 16.
Solution: X= 10 or 32/3.
16-0.5x 10 = 1 1;
15-0.5x(32/3)=29/3。
So the waist length of an isosceles triangle is 10 or 32/3cm, and the base length is 1 1cm or 29/3cm.