Answer :

Answer:

60

Step-by-step explanation:

Let's identify what the sequence could be:

100 + 20 = 120

120 - 60 = 60

60 + 20 = 80

80 - 40 = 40

It looks like it is add 20,  and then subtract the next number by half of itself.

Therefore, the next number is 40+20=60.