first to know how many guests they will have we need to sum the 40 guests with the 15 drop-in guests, and these ones count as half a guest so:
40+15/2= 47.5 guests
and now to solve how much of each food will they need you to need to divide the amount of each item by 19 (because is for 19 guests) and then multiply by the total of guests they will have: 47.5 so:
-Fried chicken
24 pieces/19 guests= 1.26 pieces per guest
1.26* 47.5= 60
So they will need 60 pieces of fried chicken
-Deli meats
so they will need 55/6 pounds of deli meats
-Lasagna
so they will need 205/8 pounds of lasagna