Step-by-step explanation:
a).
n! is

(n-3)! is

If we divide the two, everything behind (n-3) will just cancel out so we would be left with only

So the answer to a is

b
Permutations formula of P(6,4) is
6!/(6-4)!, or 6!/2!.

Then we divide by 4!

The answer to b is 15
The product of three and a number (3n) is 12 more than (=12 +) the sum of the number and 26 (n + 26). Put all of those together.
2n = 12 + n + 26 Combine like terms. (12 + 26)
2n = 28 + n Subtract to get the variables together. (2n - n)
n = 28
Answer:
6
Step-by-step explanation: