Smart Work Vs Hard Work|How to Study more in less time

When A alone does a piece of work , he takes 25 days more than the time taken (A+B) to completes that particular work, while B alone takes 49 days more than the time taken by (A + B) to finish the same work. A andBtogether will take what time to finish this work?

Time taken by A to complete a work is 7 days more than the time taken by B to complete the same work. Working together they can complete the work in 12 days. In what time can A alone complete the work ?

When A alone does a piece of work , he takes 16 days more than the time taken by (A+B) to complete the work, while B alone takes 9 days more than the time taken by (A + B) to finish the work. What time,AandBtogether will take to finish this work?