This is probably easy but i'm not smart and don't know what else to do i know this is the correct formula it's just confusing to me because there're three numbers and i'm just really dumb.

First off, don't put yourself down. You'll get it eventually. It takes a different amount of time for everyone :) ♡

Area of a right triangular prism = 1/2(2B) + Ph
The 1/2 and 2 cancel each other out: B + Ph.

Base of the triangular prism: 3 × 4 = 12 cm²

Perimeter of the base (use the Pythagorean Theorem →a² + b² = c²← to figure out the missing side; hypotenuse): 3² + 4² = c²
                                                    9 + 16 = c²
                                                    √25 = 5
                                                    3 + 4 + 5 = 12 cm

Height of triangular prism: 1 cm

Plug these numbers into the formula (B + Ph):
(12 + 12×1) = 24 cm²

The area of the right triangular prism is 24 cm².