Answer:
See explanation
Step-by-step explanation:
The question has missing details, as the diagram of the prism is not shown.
However, I'll solve using a general rule.
The volume of a triangular prism is:

Where



Take for instance:



The volume is:



Another instance (see attachment).
From the attachment:



The volume is:



This is what it shows for the solution. Hope this helps.
Alright, it went 1 to the right and down 2 times.
So for point B, you calculate the opposite.
Point B goes 1 left while going up by 2.
(9 - 1, 3 + 2) = (8, 5)
Pre-image point A is (8, 5)