What was the Sat 21 Aug time for the rider whose Tues 24 Aug time was 20' 38.40 109.680mph?
create table table_26986076_6 (sat_21_aug varchar, tues_24_aug varchar, PRIMARY KEY (sat_21_aug))
select sat_21_aug from table_26986076_6 where tues_24_aug = "20' 38.40 109.680mph"