Question

Four more than twice a number is seven more than the number. What is the number?

Answer 1

Since you are dealing with an unknown number, the first step is to choose a variable (a letter) to represent the unknown number.
Please choose a variable.

Answer 2

x is a common choice.
n is also used often.
You can choose one of those or any other letter.

Answer 3

Have you chosen a variable?