Answer:
5+2x14-9-1
5+28-9-1
38-9-1
29-1
28
We have two right triangles and three different rectangles.
The formula of an area of a right triangle:

l₁, l₂ - legs
We have l₁ = 20cm and l₂ = 21cm. Substitute:

The formula of an area of a rectangle:

l - length
w - width
We have:
rectangle #1: l = 22cm, w = 29cm

rectangle #2: l = 22cm, w = 21cm

rectangle #3: l = 22cm, w = 20cm

The total Surface Area of the triangular prism:

Multiply $530.40 by 3/4. You get the equation

If you simplify this, you get the solution of $397.80
$397.80