EXPLANATION :
We will calculate the areas of each face.
Front :
A triangle with a base of 6 and a height of 4
The area is :
[tex]\begin{gathered} A=\frac{1}{2}bh \\ \\ A=\frac{1}{2}(6)(4)=12\text{ }cm^2 \end{gathered}[/tex]Back :
Same face with the front, so the area is also 12 cm^2
Right :
The right side is a 5 x 3 rectangle.
The area is 5 x 3 = 15 cm^2
Left :
The left side is the same as the right side, so the area is also 15 cm^2
The total area is 12 + 12 + 15 + 15 = 54 cm^2