ith technology, we found that

x = 4,

y = 2,

and

z = 6;

moreover, we know that x, y, and z are, respectively, the numbers of Airbuses, Boeing-767's, and Boeing Dreamliners to be ordered. The number of planes of each model to be bought are as follows.

Airbus A330-300sBoeing

767-300ERsBoeing

Dreamliner 787-9s