Looks like you just evaluated the summand for the given value of

, whereas the question is asking you to find the value of the sum for the first

terms.
Let

. Then

is the

th partial sum.

happens to be the first term in the series, which is why that box is marked correct:

But the next partial sum is not correct:

and this is not the same notion as the second term (which indeed is 0.75) in the series.
Your answer can be anything in the form y = mx+8 where you replace m with any real number.
You start with y = mx+b, and then replace the b with the y intercept 8.
The y intercept is where the polynomial crosses the y axis.
The value of m does not matter. So you could have y = 2x+8 or y = 3x+8 for instance. Replace m with whatever your favorite number is.
$20 a month. if u subtract the amount that she started with from $85, you get $60. $60 divided by 3 months is $20 a month
The number of ways to arrange the 5 writings in a row is 5! = 5 * 4 * 3 * 2 * 1 = 120 ways.
There is only 1 way to arrange the writings from oldest to newest.
Therefore, the probability is 1/120.