When the number of people increased by 10, the caterer charged an additional $80. Therefore, we estimate that the cost per person is $8. In order to verify:
$8/person * 15 people = $120. True. $8/person * 25 people = $200. True.
Therefore, if we let x represent the number of people being cater for and y represent the cost, the equation to model the situation is simply y = 8x.
