I'm so sorry for the late answer!
(a) Rectangular container
There are 3 pairs of congruent sides. Each side's area can be solved by multiplying either 12, 8, or 3. Then because for each side, there is another side that is exactly the same, we can multiply by 2.
(2*12*8) + (2*12*3) + (2*8*3) = 312
(b) Surface Area of a cylinder is
We know that r is 2 and that the whole expression is equal to 312.
Plug 2 back into the equation and set it equal to 312.
The height of the cylinder has to be around 23 inches.
(a) Rectangular container
There are 3 pairs of congruent sides. Each side's area can be solved by multiplying either 12, 8, or 3. Then because for each side, there is another side that is exactly the same, we can multiply by 2.
(2*12*8) + (2*12*3) + (2*8*3) = 312
(b) Surface Area of a cylinder is
We know that r is 2 and that the whole expression is equal to 312.
Plug 2 back into the equation and set it equal to 312.
The height of the cylinder has to be around 23 inches.