10C4 represent the Combinations of 10 objects taken 4 at a time.
The formula for nCr is:

In the given case, n=10 and r=4. Using these values we get:

This means we can make 210 combinations of 10 objects taken 4 at a time.
Answer:
$25.20
Step-by-step explanation:
First, take the 50% off the sales price:
($48)*(-0.50) = -$24.
($48 - $24) = $24 sale price.
Tax on $24 is ($24)*(0.05) = $1.20
Add the price and sales tax:
$24 + $1.20 = $25.20
I don't know what the graft is
Point form: (-2,-3)
Equation form: x=-2, y=-3