Melody

$$\\FV=PV(1+r)^n\\
$rearranging we get$\\
PV=\frac{FV}{(1+r)^n}\\\\
FV=2860\\\\
r=\frac{8.5\%}{2 }= 0.0425\\\\
n=3\frac{7}{12}*2 =7 \frac{1}{6}$$

Now just plug the number in :)

You have both assumed that these are combinations - and you are most likely correct BUT

Couldn't those be vectors?

$$\begin{pmatrix}
16 \\
4
\end{pmatrix}
&-
\begin{pmatrix}
16 \\
12
\end{pmatrix}&=
\begin{pmatrix}
0 \\
-8
\end{pmatrix}$$

I purposely did not go further with my calculatations.

I wanted to show how i would do it without using any high level calculators.    

$${\mathtt{968}} \,{mod}\, {\mathtt{44}} = {\mathtt{0}}$$

there is not remainder

Good one Chris  :))

you need to use brackets

sqrt(144/4)

$${\sqrt{{\frac{{\mathtt{144}}}{{\mathtt{4}}}}}} = {\mathtt{6}}$$

I want brackets here please.

I think this is it

1)  there are 4 choices for the first row, the X can go anywhere.    Just put your X in

2)  There are only 2 choices for the next row because it cannot go in the same box as the first one did.

3)  There are 2 choices for the next row because it can go in either box but it cannot go under either of the 2 x's that are already there.

4)  There is only one possibility left for the last row

so the number of possibilities is        4*2*2*1=16

Use the compoound interest formula but remember that

n is the number of compounding periods =  30

and

r is the interest rate as a decimal for each of these.        0.058/12 = 0.00483  repeater

Now just plug the numbers in

$$FV=PV(1+r)^n$$