Chapter 1 - Foundations for Algebra - 1-4 Properties of Real Numbers - Got It? - Page 24: 1

Both of the sides are equal: $ X + 12 = X + 12 $ Subtract 12 from both sides $ X = X $ Subtract X from both sides $ 0 = 0 $ The number 0 is equal to 0 Therefore both sides are equal

$ X + 12 = X + 12, $ Subtract 12 from both sides, $ X = X, $ Subtract X from both sides, $ 0 = 0, $ The number 0 is equal to 0, $ Therefore both sides are equal