When a number is decreased by $20 \%$ of itself, the result is 120 . What is the number? The number is

Step 1 ：Let's denote the number we are looking for as x. According to the problem, x decreased by 20% of itself is equal to 120. This can be written as an equation: \(x - 0.2x = 120\).

Step 2 ：We can solve this equation to find the value of x.

Step 3 ：The solution to the equation is 150, which means the original number is 150.

Step 4 ：Final Answer: The original number is \(\boxed{150}\).