2. What is the \( \% \mathrm{H}_{2} \mathrm{O} \) in each of these hydrated salts Magnesium Sulfate Copper(II) Sulfate 3. Based on the \( \% \mathrm{H}_{2} \mathrm{O} \) in the previous question and on your experimental results, which hydrated salt is your unknown?

\[ A=\left[\begin{array}{ll}2 & 1 \\ 5 & 3\end{array}\right], B=\left[\begin{array}{rr}3 & -1 \\ -5 & 2\end{array}\right] \] \( A B=\left[\begin{array}{ll}2 & 1 \\ 5 & 3\end{array}\right]\left[\begin{array}{rr}3 & -1 \\ -5 & 2\end{array}\right]=\left[\begin{array}{rr}6+\square \\ 15+\square & \square \\ \text { To show that } B \text { is the inverse of } A \text {, we need to show that } A B=I=B A\end{array}\right. \) \( B A=\left[\begin{array}{rr}3 & -1 \\ -5 & 2\end{array}\right]\left[\begin{array}{ll}2 & 1 \\ 5 & 3\end{array}\right]=\left[\begin{array}{rr}6+\square+\square \\ -10+\square & \square\end{array}\right]=\square \)

\( \left.\begin{array}{l}A=\left[\begin{array}{ll}2 & 1 \\ 5 & 3\end{array}\right], B=\left[\begin{array}{rr}3 & -1 \\ -5 & 2\end{array}\right] \\ \text { To show that } B \text { is the inverse of } A \text {, we need to show that } A B=I=B A \text {. } \\ A B=\left[\begin{array}{ll}2 & 1 \\ 5 & 3\end{array}\right]\left[\begin{array}{rr}3 & -1 \\ -5 & 2\end{array}\right]=\left[\begin{array}{rr}6+\square+\square \\ 15+\square & \square\end{array}\right]=\square \\ B A=\left[\begin{array}{rr}3 & -1 \\ -5 & 2\end{array}\right]\left[\begin{array}{ll}2 & 1 \\ 5 & 3\end{array}\right]=\left[\begin{array}{r}6+\square+\square \\ -10+\square\end{array}\right]=\square \\ \square\end{array}\right] \)

(i) Graph the solution set of \( C \) of \( 15-4 x>-1, x \in N \).

13. Haley was asked to solve this system of equations: \( \begin{array}{l}-2 x+5 y+3 z=-25 \\ -4 x-3 y-8 z=-39 \\ 6 x+8 y-5 z=14\end{array} \) If Haley uses a matrix what number would be in position row 2 , column 3

You own 16 CDs that are stored in a box. You have decided to display 6 of them on a shelf. One at a time, you randomly select a CD from the box and place it on the shelf until there are 6 CDs on the shelf. What is the probability that the CDs on the shelf end up in alphabetical order? Write your answer as a simplified fraction. The probability that the 6 CDs on the shelf are in alphabetical order is