Question

what is the total surface area of a rectangular prism that is 19 inches long, 9 inches wide, and 7 inches tall

Answer 1

check the picture below.

so as you can see, the box is simply 6 rectangles stacked up to each other at the edges.

so we can simply get the area of each rectangle and sum them up and that's the area of the rectangular prism.

$\bf \stackrel{\textit{front and back}}{2(19\cdot 7)}+\stackrel{\textit{left and right}}{2(9\cdot 7)}+\stackrel{\textit{top and bottom}}{2(19\cdot 9)}\implies 266+126+342\implies 734$