A and B together and B alone: time for A alone

The same question, asked 2 times: CDS 1 2017*, CDS 2 2018. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
CDS 1 2017
28 $A and B working together can finish a piece of work in 12 days while B alone can finish it in 30 days. In how many days can A alone finish the work ?$
Tap an option to check your answer.
Question 2
CDS 2 2018
44 $X and Y together can finish a job in 6 days. X can alone do the same job in 12 days. How long will Y alone take to do the same job ?$
Tap an option to check your answer.