Answer:
I think it is 35.
Step-by-step explanation:
Because I think what you do is subtract every number by each other for example 9 minus 10, 11 minus 15, 13 minus 20 so on and so on and then when you get all the answers add them all together and that's your answer. But I don't know so if it is wrong dont get mad at me because I'm only in 6th grade.
