The Atomic number is the number of protons in an atom. The mass number is found by taking the sum of all of the protons and neutrons in an atom and adding them together.
However, the mass number you calculate will always be slightly different than the mass on the periodic table because the...
This needs to be rewritten I think. But as it stands the answer seems to be 1 - 3/x^2
PEMDAS (Please Excuse My Dear Aunt Sally) Parenthesis, Exponents, Multiply and Divide Left to right, Add and Subtract left to right.
(11-6)^2 + 6*2 - (3+3)^2
P 1.) 5^2 + 6*2 - 6^2
E 2.) 25 + 6*2 - 36
MD 3.) 25 + 12 - 36