Finding Height of A Cylinder..

The cylinder pictured below has a surface area of 660cm2.
(diameter=14/ radius=7)
that's all it shows in the diagram:

Use the following formula to determine the height of the cylinder:
Surface Area = 2(pi) RADIUS SQUARED + 2(RADIUS)(HEIGHT)

Quote: "Surface Area = 2(pi) RADIUS SQUARED + 2(RADIUS)(HEIGHT)".
Well, that's not right for a start!
The curved surface area (CSA) of a right cylinder is 2.π.r.h; r = radius, h = height.
The other part, 2.π.r², for the total area of the cylinder's ends is correct, though.

So we have Total Surface Area (TSA) = 2.π.r² + 2.π.r.h.
To keep what follows simple, I'll replace the term 'TSA' by 'A':
A = 2.π.r² + 2.π.r.h.

So now do a bit of algebraic re-arrangement:
A - 2.π.r² = 2.π.r.h,
(A - 2.π.r²) / 2.π.r = h,
(A/2.π.r) - r = h.

Now put in the numbers.
We have d = 14 (presumably cms.), so r = 7; A = 660 cm².
660 / (2.π x 7) - 7 = h,
660 / 44 - 7 = h,
15 - 7 = h,
so, h = 8.