Step-by-step explanation:
Step 1. Of 20 bands, only 8 will play at the concert. Let n be the total number of bands, and r be the number of bands that will play:

Step 2. We are asked to use the nPr formula, which is a formula to calculate the number of permutations when we have n total objects and we take r at a time:

Step 3. Substitute the known values of n and r to find the answer:

Simplifying the result:

We expand the factorial expressions:

12! on the numerator cancels with 12! on the denominator:

The result is:

Answer:
