Problem 1: How would the appearance of your spread plate change if the concentration of bacteria in the mixed culture was 1000X higher than the one you used? How about 1,000,000X lower?
Problem 2: How would the appearance of your streak plate change if the concentration of bacteria in the mixed culture was 1000X higher than the one you used? How about 1,000,000X lower?
Problem 3: If you intended to isolate single colonies from a mixed culture, but after incubation you observe a lawn of bacteria, what went wrong? And what would you do to get single colonies from your lawn?