Check the forward differences of the sequence.
If
, then let
be the sequence of first-order differences of
. That is, for n ≥ 1,

so that
.
Let
be the sequence of differences of
,

and we see that this is a constant sequence,
. In other words,
is an arithmetic sequence with common difference between terms of 2. That is,

and we can solve for
in terms of
:



and so on down to

We solve for
in the same way.

Then



and so on down to


where is the figures to solve.
It’s A, as you can tell from my picture
Mrs Carson gives the better deal, this is becuase when i set up an inequality 48/6 and 67.50/9, i divided 48 by 2 then added 24 to 48 so i could get them both so i can see what they give, so Mrs Carson gives 72 dollars every 9 hours and thats better than 67.50.