Answer:
10
Step-by-step explanation:
The first thing we must do for this case is find the number of total guitarists.
We have then:

We now look for the relationship between the number of guitarists playing jazz alone to the total number of guitarists.
We have then:

Where,
x: number of guitarists playing jazz alone
From here, we clear the value of x.

Then, the number of guitarists who play classical solo is:

Answer:
30 guitarists play classical solos in the contest
Answer:
a. 5,040 ways
b. 210 ways
Step-by-step explanation:
a) We want to pick 4 numbers out of 10 given that orders matter
If orders do matter, it will be a permutation problem
Mathematically;
n P r = n!/(n-r)!
In this case, n is 10 and r is 4
Thus, we have it that;
10 P 4 = 10!/(10-4)! = 5,040
b) if orders do not matter
It will be a combination problem
n C r = n!/(n-r)!r!
n = 10 and r = 4
10 C 4 = 10! /(10-4)!4!
= 210
it would be 40000000 because there there are 7 zeroes and then you and then you multiply the two twos together and then put it in the front.