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Problem
Subtracting from 1000 with borrowing is error-prone.
Solution
Subtract each digit from 9, except the last digit which you subtract from 10.
Benefit
No borrowing needed, eliminates most common subtraction errors.
Example
1000 - 456:
9-4=5
9-5=4
10-6=4
Answer: 544
1000 - 723:
9-7=2
9-2=7
10-3=7
Answer: 277