



 
Hi there. Start crossing off members of the group. If 3 have neither, that means there are 153 = 12 members of the group left. 7 of those members have red balls. That leaves 127 = 5 members who have just blue balls. But you've been told there are 8 members with blue balls, so 85 = 3 more members must have blue balls and the only members who could have them already have red balls. Cheers,  


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