Answer:
$100 or y = 7.5x + 30
I used x as it represents the cost of each friend and can be used to solve the total number of friends possible.
She can have 9 friends at her party
Explanation:
y = 7.5x + 30
Total Amount + Cost per Friend + Total Cost of Pizza
100 = 7.5x +30
subtract 30 from each side
70 = 7.5x
divide each side by 7.5
9.33 = x
Always round down to the nearest whole in human examples!