A4-digit number ends in 3. if you put the number 3 in the first position, the number will decrease by 738. find the original 4-digit number.

4153

Step-by-step explanation:

Let the original number be    [a is the number of thousands, b - the number of hundreds, c - the number of tens, 3 - the number of ones]

If you put the number 3 in the first position, the number will be

New number is 738 less than old number.

When you subtract from 3 some number c and get 8, then you have to lend one ten and subtract this number c from 13. So, 13-5=8. Thus, c=5. Remember about lending! Now when you subtrat from 4 (not 5 because of lending) some number b and get 3, then b=1. Now when you subtract from 1 some number a and get 7, then you have to lend 1 from the number of thousands and subtract a from 11 to get 7, thus 11-4=7 and a=4.

We get initial number 4153 and  rewritten number 3415. Check the difference:

4153-3415=738

there is only one way to arrange all the eight relative to each other because they are not distinct. we have

now there are nine places to place an (and not more than one in one place).   because we have four symbols, we need to choose four of these nine places to insert an . order does not matter because the are not distinct.

thus there are 1 · c(9,4) ways, or, if we calculate it,

thus there are 126 ways to form such "words."