On Monday students saw 15 birds at the feeder other days they 12 13 19 and 20 They fewer on Wednesday than Friday most How many did see o?

Let x be the number of birds they saw on Wednesday. Then, we know that:

15 + 12 + 13 + 19 + 20 + x = 89

x + 69 = 89

Therefore, x = 20.

On Wednesday, they saw 20 birds.