Explanation:
To find the correct answer for the unsolved equation, we need to identify the pattern or rule being followed in the given system of equations.

Pattern:
Let's analyze the given equations and identify the pattern:

Equation 1: 728 - 213 = 2
Equation 2: 549 - 123 = 2
Equation 3: 459 - 164 = ?

In each equation, we are subtracting two numbers and getting the result as 2. To understand the pattern, let's break down the numbers:

Equation 1:
- 728 can be written as 700 + 20 + 8
- 213 can be written as 200 + 10 + 3

Equation 2:
- 549 can be written as 500 + 40 + 9
- 123 can be written as 100 + 20 + 3

Equation 3 (unsolved):
- 459 can be written as 400 + 50 + 9
- 164 can be written as 100 + 60 + 4

Pattern Identified:
From the breakdown of the numbers, we can observe the following pattern:
- The first digit of the first number is multiplied by 100 and added to the second digit of the second number.
- The second digit of the first number is multiplied by 10 and added to the second digit of the second number.
- The third digit of the first number is added to the third digit of the second number.

Applying the Pattern:
Using the identified pattern, let's solve the unsolved equation:

Equation 3:
- 459 - 164
- (400 + 50 + 9) - (100 + 60 + 4)
- (400 - 100) + (50 - 60) + (9 - 4)
- 300 - 10 + 5
- 295

Therefore, the correct answer for the unsolved equation 459 - 164 is 295.

Conclusion:
The correct answer for the unsolved equation 459 - 164 is 295. This answer is obtained by applying the identified pattern in the given system of equations.