To calculate the area fo a triangular prism you have to calculate the are of each side of the prism ad add them.
The triangles are right triangles, their base is b=6in and their heigth is h=8in
The area of each one of them can be calculated as
Since there are 2 of them and are equal, you have to multiply it by 2, so the area of both triangles is
Next you have to calculate the ares of the rectangular faces:
One face has a length of 12 in and a width of 10 in, its area is:
The second face has a width of 8in and a length of 12 in
And the third face has a width of 6in and a length of 12 in
Now all that is left to do is to add all calculates areas to determine the area od the prism
The option that best represents the area of the prism is C. 284in²