In $10$ years the product of Melanie's age and Phil's age will be $400$ more than it is now. Find what the sum of Melanie's age and Phil's age will be $6$ years from now.
1. Let \( A \) be Melanie's age now.
2. Let \( B \) be Phil's age now.
3. According to the problem, in 10 years, the product of their ages will be 400 more than it is now. This can be written as:
   \[
   (A + 10)(B + 10) = AB + 400
   \]
4. Expanding the left-hand side of the equation:
   \[
   AB + 10A + 10B + 100 = AB + 400
   \]
5. Subtract \( AB \) from both sides:
   \[
   10A + 10B + 100 = 400
   \]
6. Subtract 100 from both sides:
   \[
   10A + 10B = 300
   \]
7. Divide both sides by 10:
   \[
   A + B = 30
   \]
8. We need to find the sum of Melanie's age and Phil's age 6 years from now:
   \[
   (A + 6) + (B + 6) = A + B + 12
   \]
9. Substitute \( A + B = 30 \) into the equation:
   \[
   A + B + 12 = 30 + 12 = 42
   \]

The final answer is \(\boxed{42}\).