12,176/24 = 1522/3 or 507 1/3
<h2><em>I believe 10.91ft but I'm not sure.</em></h2>
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.
It tells you how temperature varies with pressure :)