Peter F. answered 04/30/20
Multi-level Elementary Math Teacher; 18 Years' Teaching Experience
There are 7 yellow apples left.
Since Bob ate 2 red apples each day, ending up with 6 left at the end, that means he ate red apples for 7 days. 7x2=14; 20-14=6.
Therefore, since Bob ate 3 yellow apples each day for 7 days: 7x3=21. 28-21=7
I hope this helps!