A Rigid Motion is a transformation that preserves length (distance preserving) and angle measure (angle preserving). Another name for a rigid motion is an isometry. A direct isometry preserves distance and orientation. Translations and Rotations are direct isometries.
So I think you have to find 11% of 24 and that is 11/100 x 24 = 2.64$. Then you reduce it to the real price 24-2.64= 21.36$ (the new prize). I might be completly wrong but I hope this helps