有一道数学题,请教大家应该怎么解. 谢谢!
Three people, A, B and C, cards on their heads. Cards are N. One of the numbers is the sum of the other two.
A
B C
A: I don't know
B: I don't know
C: I don't know
A: I know, 65.
Question: what's the sum of all three?
我好像连题目都没读明白. 汗 ...