We can use the formula for permutations to solve this.
[tex]p(n, r) = \frac{n!}{(n-r)!}[/tex]
First we plug the numbers into the formula.
[tex]p(4, 2) = \frac{4!}{(4-2)!}[/tex]
Simplify.
[tex]p(4, 2) = \frac{4!}{2!}[/tex]
Expand the factorials.
[tex]p(4, 2) = \frac{4*3*2*1}{2*1}[/tex]
Cancel the 2*1.
[tex]p(4, 2) = 4*3[/tex]
Finally, multiply 4*3 and find the final answer, which is 12.
