I believe the answer you are looking for is 840 ÷ 17.5 which is 48 acres.
QUESTION 1: The answers are GEOMETRIC and 256.
QUESTION 2: The answer is 3.
QUESTION 3: The answer is tn = -9n + 42
QUESTION 4: The answer is tn = 2n + 4
QUESTION 5: The answer is tn = 1*3^(n-1) (THE SECOND CHOICE)
QUESTION 6: The answer is tn = 1*(1/2)^(n-1) (THE THIRD CHOICE)
QUESTION 7: The answer is 26.
QUESTION 8: The answer is 3.
Part A: After 9 days the radius of algae was approximately 12.81 mm. The reasonable domain to point is (0,9).
Part B: The 9 on the y-intercept represents the amount of algae the experiment started with.
Part C: (12.81-10.12)/7=0.38