5/7 seated in covered area
2/7 seated in open area
600o = 2/7 since you know 6000 were not included in the 5/7 seated in the covered area, 6000 is 2/7 of the spectators. 6000/2 = 3000 = 1/7
since 3000 is 1/7 and you need to find 7/7 multiply 3000 x 7 = 21,000 = 7/7
21,000 total spectators