Bunuel wrote:

Ashley paid 5 dollars for 1 notebook and 1 pencil. If both prices were integers, how many pencils did Ashley buy if she paid 93 dollars for the pencils and for 15 notebooks?

A. 6.

B. 16.

C. 18.

D. 21.

E. 26.

N + P = 5 - (i)

GIven that both the prices are integers.

15N + xP = 93, x = ?

From (i), we know that

15N + 15P = 75

Therefore

(x - 15)P = 18 (ii) and both x and P are integers.

From (i), we also need to keep in mind that both N and P fall in the range (1, 4)

Checking the options for (ii)

A. 6. This will give a negative value. INCORRECT

B. 16. If x = 16, P = 18. INCORRECT

C. 18. If x = 18, P = 6 INCORRECT

D. 21. If x = 21, P = 6.

CORRECTE. 26. If x = 26, P is not an integer. INCORRECT

Correct Option: D