Complete Map 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 ?

If man A complete a work in 10 days & man B complete the same work in 15 days , in how many days the work is completed if they work together ?

Working 5 hours a day. A can' complete a work in 8 days and working 6 hours a day, B can complete the same work in 10 days. Working 8 hours a day, they can jointly complete the work in

A can complete a work in 'm' days and B can complete it in 'n' days. How many days will it take to complete the work if both A and B work together?