SOLUTION: http://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.673004.html can someone please explain this question? what do the C's

Question 675607: http://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.673004.html
can someone please explain this question? what do the C's mean in the first two lines?
thanks.
Answer by KMST(5364) (Show Source): You can put this solution on YOUR website!
The C's are part of a symbol that means combinations.
Unfortunately different names and symbols are used in different textbooks.
To make matters worse, the symbol is hard to render, meaning that what you would write with pencil and paper may be impossible to type.
"10C2" meant the number of combinations of 10 taken 2 at a time,
meaning the number of sets of 2 girls that could be made from the 10 girls in the class.
That was
"(10+x)C2" meant the number of combinations of 10+x taken 2 at a time,
meaning the number of sets of students that could be made from the 10 girls plus x boys in the class.
That was calculated as .
Then, the ratio of all the number of possible sets of 2 girls,
divided by number of all possible sets of 2 pupils,
was set as equal to the probability of having 2 girls as the set of 2 pupils selected at random: 0.15.
= --> --> -->
Then, dividing both sides of the equal sign by ,
-->
And cross-multiplying, or going through a couple of dividing/multiplying both sides of the equal sign by the same number,
-->
RELATED QUESTIONS
Could a tutor please verify whether the following solution is correct?... (answered by ikleyn,math_tutor2020)

Hi, I can't understand the answer as explained in the link below.... (answered by lynnlo,MathTherapy,josgarithmetic,greenestamps)

Ms. Ikelyn, I'm confused about the problem here:... (answered by ikleyn)

The number of pairs of integers (x,y) that satisfy both x^2 + y^2 ≤ 36 and y= -4 is...? (answered by ikleyn,math_tutor2020)

Regarding my last question... (answered by ikleyn)

The positive integers greater than 3 are arranged in rows and columns as illustrated. In... (answered by math_tutor2020,ikleyn)

How does someone tell you when an answer you provided is wrong. The answer at this URL... (answered by Alan3354)

Shortly after 5 o'clock, when the minute hand and the hour hand of the clock made a 90... (answered by ikleyn)

On the below link, Ms.Ikelyn has provided a solution to a problem. However, I would like... (answered by ikleyn)