This is asking how many ways can we choose 13 songs from a set of 25.
The formula is:
n! / r! * (n -r)! =
25! / 13! * 12! which equals
25 *24 *23 *22 *21 *20 *19 *18 *17 *16 *15 *14 *13! divided by
13! * 12! which equals
25 *24 *23 *22 *21 *20 *19 *18 *17 *16 *15 *14 divided by
12* 11* 10* 9* 8* 7* 6* 5* 4* 3* 2*
which equals
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2,490,952,020,480,000
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divided by
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479,001,600
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</span>
and that equals
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5,200,300
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</span>
combinations
Here's a combination calculator to check your work:
http://www.1728.org/combinat.htm
It is 42 because 63 x 2/3 is 42.
Well, I don't really understand if it is 30 or 305 because of the spacing but I'll answer both. If it is 5y+305, just divide the whole equation by 5 and it will look like this (<u>5y+305)</u> then the factor would be 5(y+61)<u>
</u> 5
If it is 5y+30 it would be just in the same process, Divide the equation by 5 and the result will be 5(y+6).
