in a group of 100 people , 50 like reading books , 20 like both reading books and listening songs . how many like listening songs ?
make a venn diagram , and enter your data . let the number of people who like listening songs be x x + 20 + 30 = 100 x = 50 so number who like listening songs = 20 + 50 = 70 answer c
add(add(20, subtract(50, 20)), 20)