To find the volume of a rectangular prism, you need to multiply its three dimensions (length, width, and height) together. In this case, Bess's rectangular prism is 12 units long, 8 units wide, and 13 units tall.
To calculate the volume:
1. Multiply the length, width, and height together:
Volume = Length x Width x Height
Volume = 12 units x 8 units x 13 units
Volume = 1248 cubic units
Therefore, the volume of Bess's rectangular prism is 1248 cubic units.