Concept:In a number series, find the missing term by identifying the repeating difference pattern.Explanation:Let the missing first term be x.The series is x,3,4,6,7.The differences are 3−x,1,2,1.The pattern alternates as +2,+1.So, 3−x=2.Therefore, x=1.Check: 1,3,4,6,7 gives differences +2,+1,+2,+1.Answer:1