Father is $42$ years old, and son has $14$ years. In how many years father will be twice as old as his son?
1. Let the current age of the father be \( F = 42 \) years.
2. Let the current age of the son be \( S = 14 \) years.
3. We need to find the number of years, \( x \), after which the father will be twice as old as the son.
4. In \( x \) years, the father's age will be \( 42 + x \) and the son's age will be \( 14 + x \).
5. We set up the equation based on the condition that the father will be twice as old as the son:
   \[
   42 + x = 2(14 + x)
   \]
6. Simplify the equation:
   \[
   42 + x = 28 + 2x
   \]
7. Subtract \( x \) from both sides:
   \[
   42 = 28 + x
   \]
8. Subtract 28 from both sides:
   \[
   42 - 28 = x
   \]
9. Simplify:
   \[
   x = 14
   \]

The final answer is \( \boxed{14} \).