Question

Can someone explain this q .

Answer 1

Check the picture below.

so let's get the surface area of it, keeping in mind that's 158 cm²

`\stackrel{ \textit{\LARGE Areas} }{\stackrel{ \textit{front and back} }{2(y)(5)}~~ + ~~\stackrel{\textit{left and right}}{2(3)(5)}~~ + ~~\stackrel{\textit{top and bottom}}{2(y)(3)}}~~ = ~~158 \\\\\\ 10y+30+6y=158\implies 16y=128\implies y=\cfrac{128}{16}\implies \boxed{y=8}`