1/12 + 1/15 = 9/60 = 3/20
20/3 = 20/3 *2 = 13 1/3 days
A can do a job in 12 days and B can do it in 15 days. A and B working together will finish twice the amount of work in days?

a: 22 1/6
b: 22 1/2
c: 22 1/0
d: 22 1/9
e: 13 1/3