We know that
[the surface area]=2*[area of the base]+[perimeter of the base]*height
[the surface area]=2*[8*2.5]+[2*(8+2.5)]*12
[the surface area]=40+252-----> 292 in²
the answer is
<span>the least amount of cardboard needed to make the cereal box is 292 in</span>²
First, you had to switch sides of equation.
And it gave us ⇒ 
Then multiply by five from both sides of equation form.
And it gave us ⇒ 
Simplify.
And it gave us ⇒ 
Next, divide by two from both sides of equation form.
And it gave us ⇒ 
Finally, simplify.
And it gave us ⇒ 
Final answer: ⇒ 
Hope this helps!
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-Charlie