Plz with this math. can't find the area of the triangular faces.

First of all, you have to find the area of both triangles:


Or just 16 because there are 2 of the same triangles.

Now you have to find the area of the 3 rectangles.

The two that are in the front are 4*3 (l*h) or 12*2 (because there are 2 congruent rectangles. The area of those rectangles is 24 square mm.

Now you find the area of the back rectangle:
5.7*3 = 17.1

Finally, you add all the found numbers to figure out the surface area.
17.1 + 16 + 24 = 57.1 square millimeters.

Hope this helped,
Loafly