15. When adding several numbers, the following errors were made: in one of the numbers, the digit 3 in the tens place was taken for 8, and the digit 7 in the hundreds place was taken for 4; in another, the digit 2 in the thousands place was taken for 9. The sum obtained was 52000. Find the correct sum.
15. The obtained sum is greater than the true one by 7 thousand and 5 tens, but less than it by three hundred. To get the true sum, you need to subtract 7050 from 52000 and add 300 to the result. Answer: 42250.