X ,Y and Z each try independently to solve a problem .If their individual probabolity for success are ¼,1/2 and 5/8 ,respectively, what is the probabolity that X and Y ,but not Z ,will solve the problem. (a) 11/8 (b) 7/8 (c) 9/64(d)5/64(e)3/64 answer (e) 能不能帮忙解释一下。为何是1/4x1/2x3/8=3/64 没有解题的思路。谢谢 | 
