can soemone tells me what this means

Question

10!
----- =45
2!*8!

i don't get the explnation points or how they got 45 out of that

Answer 1

It is the formula for "combinations"
In this case it could mean:

There are 10 people that all shake hands with each other. How many handshakes are there?
or
given 10 different elements, how many subsets can be found that contain 2 elements?

8! means 1x2x3x4x5x6x7x8 = 40320

Several notations are used
C(n,r) = _nC_r
= n!/(r!(n-r)!)

so C(10,2) = 10!/(2!8!)
= 3628800/(2*40320) = 45