7/8∵随机变量服从X~B(2,P),∴P(X≥1)=1-P(X=0)=1-C 02 (1-p) 2 =34 ,解得p=12 .∴P(Y≥1)=1-P(Y=0)=1-C 33 (1-p) 3 =1-18 =78 ,故答案为78 .