Question: a alone can complete work in 16 days?
Answer: A completes a work in 16 days. So percentage of work done by A per day is 100/16 which is 6.25%. After 12 days the percentage of work completed will be (14.58*6) which is 87.48. On 13th day A will start to work, hence after 13 days work completed will be 87.48+6.25 = 93.73.