B=boys, G=girls, A=adults
B/G=4/5, G/A=7/2
So B=4G/5 and A=2G/7.
Ratio: B:G:A=4G/5:G:2G/7 that is: 4/5:1:2/7.
Multiply each ratio by the LCM of 5 and 7:
28:35:10.
Ratio of kids to adults: (28+35)/10=63:10.
146 people: 28/73×146=56 boys,
35/73×146=70 girls, (70 girls in a class of 146 people)
10/73×146=20 adults.
Kids=126.