Find the solution of the following equation if the replacement set is {0, 1, 2, 3}.
Take each number from the replacement set, plug it into the equation, and simplify.
You will find that only the number 3 makes the equation true.
4n – 7 
= 
5 


4(3) – 7 

5 
Plug in n = 3 

12 – 7 

5 
Multiply 

5 
= 
5 
Subtract 
In contrast, all the other numbers in the replacement set make the equation false. For example, try the number 2.
4n – 7 
= 
5 


4(2) – 7 

5 
Plug in n = 2 

8 – 7 

5 
Multiply 

1 
≠ 
5 
Subtract 
Since the equation is true when you plug in 3, the solution is 3.