1. Invitations were sent to 55 relatives for a family get-together. Only 50 relatives came. How many relatives did not come?   2. Mark weighs 21 kg. His mother is 51 kg. How much more is his mother's weight (in kg)?   3. Mr. Gates will be 40 next year. His son is 32 years younger than him. How many years old is his son at present?   4. A family party has 45 adults, 4 boys, and 15 girls. How many more adults are there at the party than children?   5. Arthur is 14 years old. His aunt is 43. How many years older than him is his aunt?