The original number that was multiply by 5 instead of 3 is 6.
The equation that can be used to represent the informatioin in the question is:
5x - 3x = 12
Where x is the original number
In order to determine the value of x, take the following steps
Combine similar terms: 2x = 12
Divide both sides by 2
x = 6
To learn more about multiplication, please check: https://brainly.com/question/3385014