Add the 3 item totals, then divide that number by 100, then, take that number and multiply by 9 (this gets the tax total). then you are going to want to add the total of the 3 items, and the tax amount, and you have your answer. do this with all the peoples items :)
The easiest way to do this would be to add up the total cost of each person's meal (for example, in the first one you would do $3.79 + $9.89 + $5.99 = $19.69).
Then turn the percentage into a decimal (put a decimal point after the number, so for example 9.0% and then move the decimal point to place to the left to turn it into a decimal. So 9% become 0.09).
Lastly, times the total amount you got from the first part to the decimal you got in the second part ($19.69 x 0.09 = 1.7703, which you rounds to $1.77)
So your tip is $1.77 for the first person. Repeat this process for each one and you can't fail, cheers!
The d value is going to be -3 because you have to compute the differences of all the adjacent terms. 2-5=-3 -1-2=-3 -4-(-1)=-3 -7-(-4)=-3 The difference between all the adjacent terms is the same and equal to -3
. Then 
, and so as 
, you have 
. The limit is then equivalent to
