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The order of operations is a set of rules used to determine the order in which calculations are done in an expression. This is crucial because performing operations in different orders can lead to different results.

In math, we follow the acronym PEMDAS:

• Parentheses
• Exponents
• Multiplication and Division (from left to right)
• Addition and Subtraction (from left to right)

Without following these rules, you might simplify expressions incorrectly which could lead to an incorrect answer. For instance, in the equation given, we see both parentheses and subtraction. According to PEMDAS, we need to handle operations inside the parentheses first before dealing with multiplication and subtraction.

Parentheses are used to group parts of an expression that need to be evaluated first. In our exercise, the expression inside the parentheses is \[4-6\].

The purpose of parentheses is to ensure those calculations happen before others, overriding the default order of operations.

To solve this, calculate the expression inside the parentheses first: \[4 - 6 = -2\]. By resolving expressions within the parentheses first, you avoid mistakes in simplification and ensure accuracy. Remember, always look inside parentheses and resolve those operations first before moving on to the rest of the expression.

Subtraction is one of the basic arithmetic operations and involves taking one number away from another. In our example, subtraction appears twice: once inside the parentheses and once outside.

First, you do the subtraction inside the parentheses: \[ 4 - 6 = -2 \].

After multiplying and arriving at \[ 2(-2) = -4 \], do the final subtraction:
\[ 23 - (-4)\]. When you subtract a negative number, it is the same as adding that number. Thus, \[23 - (-4)\] becomes \[23 + 4 = 27\].

Understanding subtraction and how it interacts with negative numbers is vital for simplifying expressions correctly. By always simplifying inside the parentheses first and keeping track of negative signs, you safeguard against errors.