Let x be the profit of a bracelet and y the profit of a necklace.
Yesterday she sold: 9 bracelets and 3 necklaces, for a profit of $144:
![9x+3y=144](https://img.qammunity.org/2023/formulas/mathematics/college/uxb3smzc7qi6c3co233d74elwjnnu156x1.png)
Today, she made a profit of $279 by selling 10 bracelets and 9 necklaces:
![10x+9y=279](https://img.qammunity.org/2023/formulas/mathematics/college/3ydmgoohifio5h3pyheaeb8ttop2smnkjj.png)
System of equations:
![\begin{gathered} 9x+3y=144 \\ 10x+9y=279 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/jz3r5f8yqj2u1o8lqtqlby4x7c9o41gfv4.png)
To solve by elimination:
1. Multiply the first equation by -3:
![\begin{gathered} -3(9x+3y=144 \\ \\ -27x-9y=-432 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/1blzo1ei2atk4xeky4v7tz35hhkk2topsf.png)
2. Add equation you get in step 1 and the second equation in the system:
![-17x=-153](https://img.qammunity.org/2023/formulas/mathematics/college/tm2tcjt6lod8gsxs7uccmge3g55g051g85.png)
3. Use the equation you get in step 2 to solve x:
![\begin{gathered} \text{Divide both sides of the equation into -17} \\ \\ (-17)/(-17)x=(-153)/(-17) \\ \\ x=9 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/bspcsliycqw9q17lzohek0a9zrs3q6rfpc.png)
4. Use the value of x to solve y:
![\begin{gathered} 9x+3y=144 \\ \\ 9(9)+3y=144 \\ 81+3y=144 \\ \\ \text{Subtract 81 in both sides of the equation:} \\ 81-81+3y=144-81 \\ 3y=63 \\ \\ \text{Divide both sides of the equation into 3:} \\ (3)/(3)y=(63)/(3) \\ \\ y=21 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4s9ly5tfk4odh76powbpr7fmco6l5pazij.png)
Then, the solution for the system is :
![\begin{gathered} x=9 \\ y=21 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/41fj4r02gw0m8amyswozslumq6la8c908g.png)
Kaylee earns a profit of $9 from every bracelet and $21 from every necklace