Which line represents a direct variation function?

Jack did 3/5 of all problems on his weekend homework before sunday. on sunday he solved 1/3 of what was left and the last 4 problems. how many problems were assigned for the weekend?

8litres of paint can cover 129.6 m². how much paint is required to paint an area of 243m²?

Students are getting signatures for a petition to increase sports activities at the community center. the number of signatures they get each day is 3 times as many as the day before. the expression 3^6 represents the number of signatures they got on the sixth day. how many signatures did they get on the first day?