If BOB have 1 Ether and Send it to alice, and at the same time send 1 lip to Eve , because the first transaction not mined yet

How i can make sure that BOB can't send double transaction after confirme the first yet ?

marked as duplicate by Lauri Peltonen, Achala Dissanayake, mirg, Jamie Hale, Community Mar 26 '18 at 20:47

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