Question

The surface are I cannot find

Answer 1

What he said is true

Answer 2

check the picture below.

so the triangular prism is really just 3 rectangles and 2 right-triangles,

now, we know the base of one of the triangles is 2.6, what's its height?

since it's a right-triangle, we can simply use the pythagorean theorem to get "h".

$\bf \textit{using the pythagorean theorem} \\\\ c^2=a^2+b^2\implies \sqrt{c^2-a^2}=b \qquad \begin{cases} c=\stackrel{hypotenuse}{5.2}\\ a=\stackrel{adjacent}{2.6}\\ b=\stackrel{opposite}{h}\\ \end{cases} \\\\\\ \sqrt{5.2^2-2.6^2}=h\implies 4.5\approx h$

so, we can now, simply get the area of both of the triangles and the three rectangles and sum them up, and that's the area of the triangular prism.

$\bf \stackrel{two~triangles}{2\left[ \cfrac{1}{2}(2.6)(4.5) \right]}~~+~~\stackrel{rectangle}{(2.6\cdot 4.3)}~~+~~\stackrel{rectangle}{(4.3\cdot 3.9)}~~+~~\stackrel{rectangle}{(4.3\cdot 5.2)} \\\\\\ 11.7+11.18+22.36\implies \blacktriangleright 45.24 \blacktriangleleft$