A two-digit number is such that the product of its digits is 20. If 9 is added to the number the digits interchange their places. Find the number.

Explanation

To solve the problem step by step, we will define the two-digit number and set up equations based on the information given in the question.

### Step 1: Define the digits of the two-digit number
Let the two-digit number be represented as \( 10y + x \), where:
- \( y \) is the digit in the tens place,
- \( x \) is the digit in the units place.

### Step 2: Set up the first equation based on the product of the digits
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