Plug n = 1 into the expression 20-9n and we get
20-9n = 20-9*1 = 20-9 = 11
So 11 is the first term of the series that we add up. Therefore the answer must be choice C, which has 11 listed as the first term added
Answer:

Step-by-step explanation:
Given: a graph
To find: the average rate of change of the amount of the element over the 10-minute experiment
Solution:
A rate of change of one quantity with respect to another quantity is known as rate of change. If y is the dependent variable and x is the independent variable then average rate of change = change in y /change in x.
From the graph,
change in x (time) =
minutes
change in y ( amount of the element) =
g
So, average rate of change = 
X is equal to -11/6 or -1.8333333333..................................
Let's look at each answer choice's words per minute:
A) 320/8 = 40
B) 600/12 = 50
C) 350/10 = 35
D) 225/5 = 45
The fastest is 50 words/min which is B
In order for us to answer this question, more information is needed.