Simplify :
`0.9+0.9xx0.9÷0.9-0.9+0.9÷0.9xx0.9`

Explanation

To simplify the expression `0.9 + 0.9 × 0.9 ÷ 0.9 - 0.9 + 0.9 ÷ 0.9 × 0.9`, we will follow the order of operations (BODMAS/BIDMAS: Brackets, Orders, Division and Multiplication, Addition and Subtraction).

### Step-by-Step Solution:

1. **Rewrite the expression**:
\[ 0.9 + 0.9 \times 0.9 \div 0.9 - 0.9 + 0.9 \div 0.9 \times 0.9 \]

2. **Convert decimals to fractions**:
Each `0.9` can be expressed as \(\frac{9}{10}\):
\[ \frac{9}{10} + \frac{9}{10} \times \frac{9}{10} \div \frac{9}{10} - \frac{9}{10} + \frac{9}{10} \div \frac{9}{10} \times \frac{9}{10} \]

3. **Perform the division and multiplication**:
- For \(\frac{9}{10} \times \frac{9}{10} \div \frac{9}{10}\):
\[ \frac{9}{10} \times \frac{9}{10} = \frac{81}{100} \]
Then divide by \(\frac{9}{10}\):
\[ \frac{81}{100} \div \frac{9}{10} = \frac{81}{100} \times \frac{10}{9} = \frac{81 \times 10}{100 \times 9} = \frac{810}{900} = \frac{9}{10} \]

- For \(\frac{9}{10} \div \frac{9}{10} \times \frac{9}{10}\):
\[ \frac{9}{10} \div \frac{9}{10} = 1 \]
Then multiply by \(\frac{9}{10}\):
\[ 1 \times \frac{9}{10} = \frac{9}{10} \]

4. **Substituting back into the expression**:
Now we have:
\[ \frac{9}{10} + \frac{9}{10} - \frac{9}{10} + \frac{9}{10} \]

5. **Combine like terms**:
\[ \frac{9}{10} + \frac{9}{10} - \frac{9}{10} + \frac{9}{10} = \frac{9 + 9 - 9 + 9}{10} = \frac{18}{10} \]

6. **Simplify the fraction**:
\[ \frac{18}{10} = \frac{9}{5} \]

### Final Answer:
\[ \frac{9}{5} \]