Being a prism, a rectangular prism has 6 faces. Although, unlike a cube, a rectangular prism does not have all equal sides. A particularly good way to see how to calculate surface area of a rectangular prism wold be to see how its net looks like.
The most elegant algebraic expression for a rectangular prism is SA= 2(lw) + 2(hw) + 2(hl)
I actually didn't know what a composite shape was at first, but I found that it's a figure that can be divided into two or more shapes. This was what Mr. B has been telling us about for the past couple of days, but I didn't know what the technical term was then.
I think the best way to calculate the surface area for composite shapes is to look at the figure from all angles and add it all up because this can apply to all composite shapes. Some composite shapes have holes and spaces in them and this can make calculating surface area for composite shapes confusing.
A figure usually has 6 faces; 3 sets of 2 symmetrical faces. Plane of symmetry are imaginary lines drawn on polyhedrons to show that both sides are symmetrical. Imagine these lines as if they cut right through the polyhedron. Symmetry helps us solve for surface area because if we see one face we know that on the opposite side there should be another face just like it. This rule usually applies for regular shapes, however. Understanding symmetry allows us to see that if one side has a measurement of so-and-so, then the other side should have that same length as well.
I hope in one way or another this has helped! Please feel free to comment! :)