1.
He fills 5/6 lb per bag.
If he fills up 6 bags, he will use 6 * 5/6 lb = 5 lb.
Since he gets peanuts in 2-lb bags, he'd use 2 1/2 2-lb bags.
If he fills double that amount, 10 5/6-lb bags, he will use 10 lb of peanuts which is exactly 5 2-lb bags.
Answer: He should buy 5 2-lb bags.
2.
Each board has length x.
He cuts 3/5 of the length.
Each leftover piece is 2/5 of the length, or 2/5 x.
When he puts together several of the leftover pieces, he has 4 times the length of the original board, or 4x.
4x/(2/5 x) = 4x * 5/2 x = 10x
He has cut 10 boards.