Let AB=AC be X and BC=y, then: x+ 1/2x=9, y+ 1/2x=8 or x+ 1/2x=8, y+ 1/2x=9.

Solve the first group with x = 6 and y = 5.

Solve the second group, X= 16/3, y= 19/3.

So the waist circumference is 6 or 16/3.