12 cups of flour is 4 times the quantity in the recipe, so 4 times as much brown sugar is needed, 4×2=8 cups of brown sugar.
Let's say the cylinders are
A = first cylinder
B = second cylinder
B has some volume, the volume is "x"
what's 7/8 of "x"? well (7/8)x
what's 8 less than that? well (7/8)x - 8
A has a volume of 216
we also know that, A's volume is (7/8)x - 8
thus
I think it’s x+1x^3... not sure if this helps