Let's split this up in sections. We have three sections.
Left
As you can tell, the side says 4 while the top says 3.
4×3
12
Middle
If you can tell, the edge says 2 inches, so to find the side of the middle, we subtract.
4-2
2×3
6
Right
It's the same as the left.
3×4
12
Let's add them together.
12+12+6
24+6
30
30 in²