Answer:
240 is the number of girls, 180 is the number of boys, 60 is how many more girls there are
Explanation:
420/7 = 60 (if you add 3 to 4 you get 7)
60*4 = 240 (240 is the number of girls)
60*3 = 180 (180 is the number of boys)
240 - 180 = 60 (This 60 is how many more girls there are)