19. Mr. sohanlal is 4 times as old as his son. Four years hence the sum of their ages will be 43 years. The present age of son is:

20. The difference between the ages of two persons is 10 years. 15 years ago, the elder one was twice as old as the younger one. The present age of the elder person is:

21. Ten years ago A was half of B in age. If the ratio of their present ages is 3:4 what will be the total of their present ages?