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1.There are 30 children in a school class.17 of them like the colour yellow. 13 of them like the colour red. 8 of them like both yellow and red. How many like neither yellow or red?
2.There are 30 children in a school class. 22 of them like yellow or red. 15 of them like yellow. 15 of them like red. How many like both red and yellow?
3.There are 100 wizards in Slytherin. 38 of them play quidditch, 49 speak parseltongue and 15 of them are in second year. 6 second years play quidditch, as do 8 parselmouths. Also, 2 second years are parselmouths. How many don't play quidditch, are not in second year and can't speak to snakes?