Hello,
As i am living near the Gers (canards du Gers), i reply.
a)
x: number of packets of ducks
3x: number of packets of chickens
x/2 : number of packets of beef
b)the costs:
x*7.5 (ducks)
3x*3.8 (chickens)
x/2*12.8 (beef)
c) and d
x*7.5+3x*3.8+x/2 * 12.8=607.2
==>25.3x=607.2
==>x=24
e)
24*7.5=180 ($) price of the ducks.