x can do a piece of work in 8 hours . y and z together can do it in 6 hours , while x and z together can do it in 4 hours . how long will y alone take to do it ?
x ' s 1 hour work = 1 / 8 ( y + z ) ' s 1 hour work = 1 / 6 ( x + z ) ' s 1 hour work = 1 / 4 ( x + y + z ) ' s 1 hour work = ( 1 / 8 + 1 / 6 ) = 7 / 24 y ' s 1 hour ' s work = ( 7 / 24 - 1 / 4 ) = 1 / 24 y alone will take 24 hours to do the work . correct option is a
inverse(subtract(inverse(6), subtract(inverse(4), inverse(8))))