Four years ago Jennifer was four times older than her daughter. After four years, Jennifer will be two times the age of her daughter. Find the present age of Jennifer and her daughter.

Karen and Barbara each have a bag that contains one ball each of the colors white, grey, orange, blue and green. Karen randomly selects a ball from her bag and puts it in Barbara's bag. Then Barbara randomly selects a ball from her bag and puts it in Karen's bag. What is the probability that after this the contents of the bag are the same as before?

If thrice the son's age in years is added to mother's age, the sum is 67. If thrice the mother's age is added to the son's age, the sum is 121. Find the age of mother and son.