If this previous statement did not make sense, consider the following:

Suppose you had a statement such as 5 + 8 = 13.  The equal sign in this statement means that this statement is an equality.  In other words, the left side and right side of the statement are equivalent in every way.   Therefore, we can always write 5+8 for 13 whenever we wish.  Here are some examples:

• We know that 6 + 8 = 14.   But we can replace 6 with 3 + 3, so (3 + 3) + 8 = 14.
• We know that 5³ = 125.  Therefore 5^{(5 - 2)} = 125 as well.
• Consider a simple algebraic statement like x + y = z.  Then (3 - 2) x + y = z.

The same holds for any equality.