The number A is a two - digit positive integer, the number B is the two - digit positve integer formed by reversing the digits of A. If `Q=10B-A`, what is the value of Q?
(1) The tens digit of A is 7.
(2) The tens digit of B is 6.

Answer

To solve the problem, we need to find the value of \( Q = 10B - A \) given the conditions about the digits of the two-digit numbers \( A \) and \( B \).

### Step-by-Step Solution:

1. **Define the Numbers**:
Let \( A \) be a two-digit number represented as \( A = 10y + x \), where \( y \) is the tens digit and \( x \) is the units digit.
Let \( B \) be the number formed by reversing the digits of \( A \), so \( B = 10x + y \).

2. **Substitute into the Equation for Q**:
We need to calculate \( Q = 10B - A \).
Substitute the expressions for \( A \) and \( B \):
\[ Q = 10(10x + y) - (10y + x) \]

3. **Simplify the Expression**:
Expanding the equation gives:
\[ Q = 100x + 10y - 10y - x \]
The \( 10y \) terms cancel out:
\[ Q = 100x - x = 99x \]

4. **Determine the Value of x**:
From the problem, we have two conditions:
- Condition (1): The tens digit of \( A \) is 7, which means \( y = 7 \).
- Condition (2): The tens digit of \( B \) is 6, which means \( x = 6 \).

5. **Calculate Q**:
Since we have determined \( x = 6 \) from Condition (2), we can substitute this value into the equation for \( Q \):
\[ Q = 99x = 99 \times 6 = 594 \]

### Final Answer:
The value of \( Q \) is \( 594 \).

---