1/12 + 1/20 = 8/60 = 2/15
15/2 = 15/2 *2 = 15 days
A can do a job in 12 days and B can do it in 20 days. A and B working together will finish twice the amount of work in days?
Options:
* 22 1/6
* 22 1/2
* 22 1/0
* 15
* 22 1/1