If a number is tripled and then decreased by 4, the result is 20. What is the number?

To find the number described in the problem, we start by setting up an equation based on the information provided. Let's denote the unknown number as ( x ). According to the problem, if we triple the number and then decrease it by 4, the resulting expression is equal to 20. This can be represented mathematically as:

[ 3x - 4 = 20 ]

To solve for ( x ), we first add 4 to both sides of the equation:

[ 3x - 4 + 4 = 20 + 4 ]

[ 3x = 24 ]

Next, we divide both sides by 3 to isolate ( x ):

[ x = \frac{24}{3} ]

[ x = 8 ]

Thus, the number is 8, confirming that this value meets the condition set by the problem. When 8 is tripled, it becomes 24, and reducing that by 4 gives 20, which matches the result specified in the question.

This approach reinforces the correct solution by demonstrating the application of basic algebraic principles, allowing you to ascertain the unknown while verifying the steps taken in the process.