2-1+4-3+6-5+8-7+....+100-99=

34.
(2-1)+(4-3)+(6-5)+(8-7)+....+(100-99)
= (1 + 1 + 1 + 1 + ......+ 1)
= 1 x (100/2)
= 50

jawaban B

35
1 + 2 + 3 + 4 + ... + 50
= (50 + 1)+(49 + 2)+...+(26+25)
= (51) x 50/2
= 51 x 25
= 1.275

jawaban B