(You forgot to add the question, but I guess you want to know the mass of the turkey for 14 people :p )
By hypothesis, 1 lb = 450g. Adam wants that each of the 14 person, get 3/4 lb. Let x be the mass of 3/4 lb in grams, using the rule of three:
1 lb --> 450g
3/4 lb --> x
x = 3/4 * 450 = 337.5
So 3/4 lb = 337.5 g
Adam wants to cook for 14 people and wants to allow 3/4 lb of turkey for each person, so 337.5 for each.
So to know the total mass of the turkey, you multiply the mass for one person by the total number of people:
337.5 * 14 = 4725
So the mass of the turkey for 14 people is 4725g, or 10.5 lb (3/4 * 14)
Hope this Helps! :)