The sum of the ages of a father and his son is 56 years. After 4 years, the father's age will be 3 times his son's age. Their ages are respectively.

A father is 5 times as old as his son. His son is 6 years old. His son is 6 years old. After how many years, will the father be 4 times as old as his son?

Select the set in which the number are related in the same way as are the number of the following set.
( 11, 16, 20)

If 2 is added to each even digit and 1 is subtracted from each odd digit in the number 621754, then what will be the sum of number/numbers not repeated in the new number?

If "÷" denotes "multiplied by", "+" denotes "subtracted from", "x" denotes "added to" and "–" denotes "divided by",then
12 – 6 + 28 × 3 ÷ 9 = ?

If two is subtracted from each odd digit and three is added to each even digit in the number 3675249 how many digits will appear twice in the new number thus formed?