Answer:
Option D 3/16
Step-by-step explanation:
Carol is cross-country skiing.
With the help of the given table we have to calculate the rate of change.
If we draw a graph for distance traveled on y-axis and tins at x-axis we find two points, ( 2, 1/6) and (3, 17/48).
Then slope of the line connecting these points will be the rate of change.
So firstly, we have to find the LCD, or lowest common denominator, of 9 and 7. To do this, list the multiples of 9 and 7 and the lowest multiple they share is going to be your LCD. In this case, the LCD of 9 and 7 is 63. Multiply x^2/9 by 7/7 and 2y/7 by 9/9:

Next, add the numerators together, and your answer will be: 
1) an = a1 + d*(n-1) => a20 = -4 + (-9)*19 = -4 - 171 = - 175
1) ---> C)
2) a81 = 20 + 4*80 = 340;
2) ---> A)
3) a12 = ?
3) ---> B) or D).