We want to calculate the surface area of the figure.
To do so, imagine that we have a cardboard box with the shape and measures of the given figure. The surface area would be the sum of the area of each of its sides. So, to solve this problem, we should calculate the surface area of each side and then add it up.
If we "cut" the box, we would get the following shapes
so, we see that we have 3 pairs of different rectangles. So, we can calculate the area of one side and multiply it by 2 so we have the total area corresponding to the sides of that shape.
We see that each figure is a rectangle. Recall that the area of a rectangle of base b and height h is given by the formula
For the first rectangle (on the left) we have that b=4 and h=3. So we have that is area is
Remember that this is the area of only one side, since there are two identical sides this these dimensions, we should multiply this number by 2. So we have
Now, for the next rectangle (in the middle), we have that b=12 and h=4. So the area would be
Since we have two, we multiply this number by 2. So we get
