a cuboid with length, width, height dimensions 5, 6, x
the value of x that makes the numerical value of the total surface area equal to the numerical value of the volume
The volume is given by
... V = L·W·H = 5·6·x = 30x
The area is given by
... A = 2(L·W + H(L+W)) = 2(5·6 +x(5+6)) = 2(30 +11x) = 60 +22x
When these are equal, we have
... 30x = 60 +22x
... 8x = 60
... x = 7.5
The desired value of x is 7.5.