explain why figure b is not the image of figure a after a reflection using line l

Answer:
See below
Step-by-step explanation:
Figure A has a square cut out into it as figure B has a trapezoid cut out into it.
A reflection is mirroring an image, this means that the image must be identical to its reflected image.
Because figure A and B have different shapes cut into it they are not identical and can therefore not be reflections.