Explanation:
that is a college question ? and you need help with that, which an elementary school student could have solved in literally 2 seconds with a calculator ?
is English the problem ? is there any other language you prefer ?
let's go through it slowly :
a "change in weight" means that the weight of the plane with everything in it (in pounds or kilograms) is different than before. "weight" means how heavy these things are.
it seems the plane started in New York and had 3,321 pounds of baggage (suitcases and other things people bring with them on a flight).
it landed in the Bahamas, and typically all the baggage is removed. that gives us 0 pounds of baggage at that point.
and then they loaded new baggage (as they got new passengers to fly from the Bahamas to New York) with 2,456 pounds.
we do not have any other information about the flight (e.g. weight of the passengers, weight of the crew, weight of the fuel, any changed parts of the plane with maybe different weights, ...).
so, our only information to measure the weight of the plane is the weight of the baggage.
and what is the difference of the weight of the baggage ?
how do we calculate differences ?
by subtracting typically the smaller number from the larger number :
3,321 - 2,456 = 865 pounds.
the change of weight of the plane is that it is now 865 pounds lighter (less heavy) than on the first flight.
please, let me know, if I need to explain more or use different words to make it clearer.