Question

The volume of a pyramid is given by the formula 

Answer 1

First I would start plugging the values into the volume equation for a pyramid. 
$84 =\frac{B (9)}{3}$
then I would multiply both sides of the equation by 3 to get rid of the dividing 
$B(9) = 252$
then I divide both dies by 9 to solve for B
$\frac{B(9)}{9} = \frac{252}{9} \\ B = 28$
Then I would just find combination s of numbers that when multiplied equal 28, I would just find all of the pairs then rule out the ones that dont have a difference of 3, the one(s) left should be your base dimensions. 

I did this and got 4 and 7
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