Problems are often answered in mathematics by solving equations. We use letters to represent an unknown number or value.
To solve an equation, we need to find what number the letter in the equation represents. That number is called the solution of the equation.
This is easy to work out when the letter you want to find is the subject of the equation. This means it is on its own on one side of the equals sign, eg:
\[x = 5 + 3\]
You can solve this by simple addition:
\[x = 8\]