If a trick always results in the same answer, what concept are we demonstrating with that trick?

If you think of a number x, double it, then add 4, what expression represents your final result after these steps?

After performing the 'Think of a Number' trick that results in always getting 2, if you wanted the result to be 3 instead, which operation can you change?

What will be the final outcome if you follow these steps: think of a number x, triple it, subtract 3, and then divide by 3?

If you think of a number, double it, add 4, divide by 2, and subtract the original number, what will the result always be?