Step-by-step explanation:
That's a terrible font! Anyways, let's work through this one.
We need to calculate the area of each of the sides of the rectangular prism and then add them together. Together this becomes the total surface area of the shape.
A helpful trick here is to remember that while a rectangular prism has 6 sides, opposite sides are equal. (The front and back cover of your favorite book have the same area, right!?)
So we only need to calculate the area of three areas, add them together, and multiply that by 2! (It's like cheating a little bit, but it will be our secret!).
Let's look at how to calculate the area of a rectange. Remember that area is length times width for a rectangle.
[tex]A = w * l[/tex]
So, the area of the first side is [tex]A_1 = 12* 8[/tex]
Second side [tex]A_2 = 12*9[/tex]
and the third side [tex]A_3 = 8*9[/tex]
If we mulply all of these and add them together, we get half of the total area. Just multiple by 2 and you've got the final answer.
Punching the keys on the calculator is up to you! :-)