Answer:
110 or 121
Step-by-step explanation:
You want a three digit number less than 130 such that the sum of the ones and hundreds digits is equal to the tens digit.
If the number is a 3-digit number, the hundreds digit is at least 1. If the number is less than 130, the hundreds digit is 1.
If the number is less than 130, the tens digit is less than 3. Since the tens digit is the sum of the hundreds digit (1) and the ones digit, for ones digit x, the sum will be ...
x +1 < 3 ⇒ x < 2
The ones digit can be 0 or 1. The corresponding 3-digit numbers are ...
110
121
The 3-digit number is 110 or 121.
