Question 1207518
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The tutor greenestamps has a great solution. It's probably the method your teacher wants you to follow. 


If your teacher allows you to use a spreadsheet then you can use the <a href="https://support.microsoft.com/en-us/office/combin-function-12a3f276-0a21-423a-8de6-06990aaf638a">Combin</a> function to find the answer very quickly.
Avoid the <a href="https://support.microsoft.com/en-us/office/choose-function-fc5c184f-cb62-4ec7-a46e-38653b98f5bc">Choose</a> function since that's something entirely different. 


<table border = "1" cellpadding = "5"><tr><td>n</td><td>A = Combin(9, n)</td><td>B = Combin(8, n-2)</td><td>A/B</td><td>Is A/B = 9/4 = 2.25?</td></tr><tr><td>2</td><td>36</td><td>1</td><td>36</td><td>No</td></tr><tr><td>3</td><td>84</td><td>8</td><td>10.5</td><td>No</td></tr><tr><td>4</td><td>126</td><td>28</td><td>4.5</td><td>No</td></tr><tr><td><font color=red>5</font></td><td>126</td><td>56</td><td><font color=red>2.25</font></td><td><font color=red>Yes</font></td></tr><tr><td>6</td><td>84</td><td>70</td><td>1.2</td><td>No</td></tr><tr><td>7</td><td>36</td><td>56</td><td>0.642857 (approx)</td><td>No</td></tr><tr><td>8</td><td>9</td><td>28</td><td>0.321429 (approx)</td><td>No</td></tr><tr><td>9</td><td>1</td><td>8</td><td>0.125</td><td>No</td></tr></table>According to the table, <font color=red>n = 5</font> will turn "9 combination n" into 126 and "8 combination (n-2)" becomes 56.
126/56 = 9/4 = 2.25
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