Question

One cylinder has a volume that is 8 cm³ less than 7/8 of the volume of a second cylinder. If the first cylinder’s volume is 216 cm², what is the correct equation and value of x, the volume of the second cylinder

Answer 1

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  

$\bf \textit{A's volume}= \begin{cases} 216\\ \frac{7}{8}x-8 \end{cases}\implies 216=\cfrac{7}{8}x-8\impliedby \begin{array}{llll} multiplying\\ by\ 8 \end{array} \\\\\\ 1728=7x-64\implies 1728+64=7x\implies \cfrac{1792}{7}=x\implies 256=x$

Answer 2

The correct answer is D) 7/8x - 8 = 216; x = 256 cm³