Answer:
The total monthly charge if one uses 769 minutes is $68.65
Explanation:
Example: If we are at x = 310, y = 45.50 and we use one more
minute, x goes up by 1, y increases by .05, putting us
at x = 311, y = 45.55. Thus, usage of 311 minutes
incurs a monthly cost of $45.55.
The y intercept is the point where x = 0.
That point on our equation is (0, 30)
This means that if zero minutes are used during the month,
the total charge for the month will be $30... the flat fee.
c) Find total monthly cost for using 769 minutes
y = .05x + 30
y = .05(769) + 30
y = 38.45 + 30
y = $68.65