Answer:
1320 ways
Step-by-step explanation:
Here we have a situation where 3 ribbons will be awarded to 3 of the 12 contestants. We can use the permutation formula, because the order of awarding the ribbons matters.
The permutation formula is:

n = 12
k = 3
Now that we have our variables, let's plug them into the formula.



So there are 1320 different ways that the contestants will be awarded.
Answer:
The x coordinates and y coordinates will switch places with each other.
Step-by-step explanation:
A' coordinates will go from (x,y) to (y,x) so the coordinates will switch.
Answer:
k = ± 4
Step-by-step explanation:
Given
x² - kx + 4 = 0 ← in standard form
with a = 1, b = - k, c = 4
The equation has equal roots, thus the discriminant
b² - 4ac = 0, that is
(- k)² - (4 × 1 × 4) = 0
k² - 16 = 0 ( add 16 to both sides )
k² = 16 ( take the square root of both sides )
k = ±
= ± 4
Using the combination formula:
n! / (r!(n-r)!)
Where n is the number of people = 12 and r is the number of jurors = 9.
12! / (9!(12-9)!) = 220 combinations.
Your plate numbers will be like

where each
is a number, and each
is a letter. Assuming you can use all numbers and letters, you have 10 possible choices for every
place (all the digits from 0 to 10) and 26 possible choices for every
place (all the letters from a to z).
So, if you multiply all the possible choices, you have

So, there is a total of

possible plate numbers with 3 letters and 3 numbers, if repetitions are allowed.