Solution - Long subtraction
8.7
Step-by-step explanation
1. Rewrite the numbers from top to bottom, aligned by their place values
| Place value | tens | ones | . | tenths |
| 1 | 5 | . | 9 | |
| 2 | . | 1 | ||
| - | 5 | . | 1 | |
| . |
2. Subtract the numbers using long subtraction method
Subtract the numbers in the tenths column from the top number:
9-1-1=7
| Place value | tens | ones | . | tenths |
| 1 | 5 | . | 9 | |
| 2 | . | 1 | ||
| - | 5 | . | 1 | |
| . | 7 |
Because the upper digit (5) in the ones column is too small to get a positive difference, borrow 1 from the digit (1) in the next number place which becomes (0) and get (15).
| Place value | tens | ones | . | tenths |
| 0 | 15 | |||
| 1 | 5 | . | 9 | |
| 2 | . | 1 | ||
| - | 5 | . | 1 | |
| . | 7 |
Subtract the numbers in the ones column from the top number:
15-2-5=8
| Place value | tens | ones | . | tenths |
| 0 | 15 | |||
| 1 | 5 | . | 9 | |
| 2 | . | 1 | ||
| - | 5 | . | 1 | |
| 8 | . | 7 |
Write 0 in the tens place.
| Place value | tens | ones | . | tenths |
| 0 | 15 | |||
| 1 | 5 | . | 9 | |
| 2 | . | 1 | ||
| - | 5 | . | 1 | |
| 0 | 8 | . | 7 |
The solution is: 8.7
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