1349
2.3
From left to right, choose the smallest digit for each position. Thus, the first digit would be 1, the second digit 0, the third digit 2, etc.
Write them as decimals, and compare. If the first digit of two numbers is equal, compare the second digit; if the second digit is equal, compare the third digit, etc.
There are a lot of possibilities. The second digit can be 2 through 6, the third digit can be 3 through 7 as long as it is larger than the second digit. What we have so far: 1 _ _ 89
The first digit can have 5 possible numbers, the second digit can have 4, the third 3, the fourth 2. 5
4284
182
Look for the first digit that is different. In this case, the first digit after the decimal point. The number that has the larger digit in this position, is larger. If the first digit is the same, compare the second digit with the second digit, the third digit with the third digit, and so forth, until you find a difference.
2.3
1155
1
1 3 4 9
The first digit has 4 choices for its digit. The second digit has 6 choices and the third has 3. The solution would simply be 4*6*3=72 three digit numbers.
Let the first and third digits be equal. Choose any other number as the second digit. 202, 919, etc.
Let's look at this digit-by-digit: The first digit can be any number 1-9: 9 choices The second digit can be any number 1-9 except the one that the first digit is: 8 choices The third digit can be any number 1-9 except the ones chosen by the first and second digits: 7 choices 9*8*7 = 504 total numbers
The first and last, and the second and third.
263