Answer:

Explanation:
In order to solve this, we are trying to find the value of 
 . Basically,
. Basically, 
 is a placeholder for a number that is unknown. Some number minus 3 is equal to 21.
 is a placeholder for a number that is unknown. Some number minus 3 is equal to 21.
Our goal is to find 
 . To do this we want to isolate
. To do this we want to isolate 
 on one side of the equation
 on one side of the equation

Let's add 3 to both sides.

Hope this helped!