9) We can see that the sticks follow an aritmetic serie, where in each step he increase 7 sticks, and we know that the first pattern has 12 steacs so the 91 patern will have:
![\begin{gathered} a_(91)=12+(91-1)\cdot7 \\ a_(91)=12+90\cdot7 \\ a_(91)=642 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/nm003kd4nuz562ald27quafht2k0uhdqdn.png)
10) Now we can made a linear equation for the squares and the triangles, So first we will work with the squares, so we can see that they increas 1 by 1 so the slope will be equal to 1 and the intercept will be 0,0 so
![y=x](https://img.qammunity.org/2023/formulas/mathematics/high-school/qx96nvxhyitmji68xu7pniht2yw5u8qwrp.png)
So if we are in our first pattern x=1 and y =1, if we are in our second pattern x=2 and y=2 so this is true for the squares.
And for the triangle they are increasing 2 by 2 so the equation will be:
![y=2x+2](https://img.qammunity.org/2023/formulas/mathematics/high-school/55a66me1fmp1rnhy3x5pu8v1e3wh5u5gdh.png)