This sentence is incomplete.
If the last digit of the 3-digit number equals the last digit of the second 2-digit number, and three times of the sum of the first and second digit of the 3-digit number equals the first digit of the second 2-digit number.
also, if that's true, then what? Maybe you just meant
The last digit of the 3-digit number equals the last digit of the second 2-digit number, and three times of the sum of the first and second digit of the 3-digit number equals the first digit of the second 2-digit number.
Also, you say
Also the sum of all the digits of the three different number is 27
This can only be true if the first number is 999
So, ignoring all the bogus clues, I get that the two numbers are
126 and 30, and the 2nd 2-digit number is 96