Final answer:
The questions involve the use of the order of operations to solve mathematical equations. The 'N' in the equations cannot be solved without a specified value, so the solutions are '8-N' and '16-N' for the two equations respectively.
Step-by-step explanation:
To solve these math problems, you must adhere to the order of operations, which is also known as BIDMAS or PEMDAS. This acronym stands for Brackets, Indices, Division and Multiplication (from left to right), Addition and Subtraction (from left to right).
For the first equation, the correct method would be '(12 + 3) - 7 - N'. Notice that we have a number, N, which is not defined. This equation will be solved up to the stage of 8-N, since without a value for N, we cannot perform any operation with it.
For the second equation, the correct method would be: '(18 - 4) + (5 - 3) - N'. As we previously discussed, without any specified value for 'N', we can't perform any operation using it, so the equation will be simplified to 16-N.
Learn more about Order of Operations