Jawabanmu

2014-06-03T13:58:49+07:00
Coba deh pake bantuan diagram venn, jumlah anak = 20 + ( 22 - 20 ) + ( 28 - 20 ) = 30 anak
2014-06-03T14:01:44+07:00
22 + 28 + 20 = X
(22 - 20  ) + (28-20) + 20 = 
2 + 8 + 20 = 30 orang