X and Y together can do a piece of work in 10 days . X is 40% more efficient than Y. X alone will complete 35% of the same work in how days?
1/x + 1/y = 1/10
1/x = 1.40 * 1/y
so x can do the job in 120/7 days
x can do 35% of the job in 35/100 * 120/7 = 6 days