What is the next sequence 1,9,20,34,51,71

Which of these choices show a pair of equivalent expressions?

The following frequency table relates the weekly sales of bicycles at a given store over a 42-week period.value01234567frequency367108521(a) in how many weeks were at least 2 bikes sold? (b) in how many weeks were at least 5 bikes sold? (c) in how many weeks were an even number of bikes sold?

Someone me what is the area of this figure? 18m 18m 8m 16m