There are 20 entries in the chess tournament. how many ways can they finish in first, second,
and third place?

6840

Step-by-step explanation:

Here, the order matters (1st, 2nd, and 3rd), so we need to use permutations.

There are 20 people who can get in first place.  After that, there are 19 people who can get in second place.  Finally, there are 18 people who can get in third place.  So:

20 * 19 * 18 = 6840

  or  

step-by-step explanation:

if the four friends split the cost, p, of the pizza evenly, then each friend pays one-fourth of the cost of the pizza.

the expression is   or  

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)