The ratio of efficiency of a master tailor and his trainee is 5:2. If they together can complete a work in 20 days, in how many days can the master tailor alone complete the work?

If 18 men working 7 hours a day can prepare 14 school uniforms in 20 days, then in how many days can 12 men working 6 hours a day prepare 18 school uniforms?

Raju alone can complete a work in 36 days, and Raj alone can complete the same work in half the time taken by Raju. How many days will they take together to complete 14 of the total work?