You first need to know your conversions:
1 pound = 16 ounces, 1 foot = 12 inches
1. so 1 pound 4 ounces = 20 ounces. Now subtract that with 13 and you should get 7 ounces
2. so 6 foot by 8 inch board = 80 inches. Now divide that with 4 and you should get 20 inches
hope that helps :)
