Best way to address this problem is to derive a linear equation representing this situation. We see that if x increases from 1 to 2, the weight of papers collected increases from 30 to 60 (lb). Thus, the slope of this line is
60-30
--------------- = 30 lb/ week
2-1
Then weight - 60 = (30 lb/week)(x - 1), or weight = 60 + (30 lb/wk)(x-1).
After 10 weeks, Ben would have collected 60 + 30(10-1) = 60 + 270 lb, or 330 lb (answer)