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:
3 meters per second
Step-by-step explanation:
15 divided by 5 = 3
3 m/s
Answer:
A 5
Step-by-step explanation:
Parts on the left have the same ratio as parts on the right.
... x/(x+5) = (x -2)/(x +1)
Multiplying by (x+5)(x+1), we get
... x(x +1) = (x -2)(x +5)
... x² +x = x² +3x -10 . . . . eliminate parentheses
... 0 = 2x -10 . . . . . . . . . . subtract x²+x
... 0 = x -5 . . . . . . . . . . . . divide by 2
... 5 = x . . . . . . . . . . . . . . . add 5