Evaluate:
`[9+(7-8)]-[(21+6)-(22-15)]`

Answer

To evaluate the expression `[9 + (7 - 8)] - [(21 + 6) - (22 - 15)]`, we will follow the order of operations, which includes solving the expressions inside the brackets first.

### Step-by-step Solution:

1. **Evaluate the innermost brackets:**
- For the first bracket: \( (7 - 8) \)
\[ 7 - 8 = -1 \]
- For the second bracket: \( (22 - 15) \)
\[ 22 - 15 = 7 \]

2. **Substitute the results back into the expression:**
\[ [9 + (-1)] - [(21 + 6) - 7] \]

3. **Evaluate the remaining brackets:**
- For the first part: \( 9 + (-1) \)
\[ 9 - 1 = 8 \]
- For the second part: \( (21 + 6) - 7 \)
- First, evaluate \( (21 + 6) \):
\[ 21 + 6 = 27 \]
- Then, subtract \( 7 \):
\[ 27 - 7 = 20 \]

4. **Now substitute these results back into the expression:**
\[ 8 - 20 \]

5. **Perform the final subtraction:**
\[ 8 - 20 = -12 \]

### Final Answer:
The value of the expression is \(-12\).