CAT/SBI PO Time and Work Hard question cracked in simple logical way

1.
1 man and 3 women and 4 boys can do a piece of work in 96 hours, 2men and 8 boys can do it in 80 hours, 2men and 3 women can do it in 120 hours. 5men and 14 boys can do it in how many hours
ans 40 hours

2
1 man and  3 women and 4 boys can do a piece of work in 96 hours, 2men and 8 boys can do it in 80 hours, 2men and 3 women can do it in 120 hours. 5 men and 12 boys can do it in how many hours

such kind of questions can be tackled by this video trick

click this video.