I’m pretty sure that the answer 783 :)
Package A = $276 for 12 tickets (2 x 6) // 276 divided by 12 = $23 per ticket
Package B = $336 for 16 tickets (2 x 8) // 336 divided by 16 = $21 per ticket
$23 - $21 = $2
Package A charges $2 more per ticket.
Subtract these 2 equations,
5x-5x +3y-y = -4-6
2y = -10
y = -5
-5 is your answer.
What you do is plug the z value (first column) into the formula (second column), and solve for y. For instance, the first one would be y = -1-2, or -3. The x would be the x in the ordered pair, and the final ordered pair would be (-1,-3). Make sense?