73. Cell Phone Plan A cell phone plan costs $3.95 per

month plus $0.07 per minute. (Assume that a partial
minute is not rounded up.)
(a) During July, a person talks a total of 50 minutes.
What is the charge?
(b) Write an equation in slope–intercept form that
gives the monthly cost C of talking on this plan
for x minutes.
(c) If the charge for one month amounts to $8.64,
how much time did the person spend talking on
the phone?

a. Per month = 3.95 + 50(.07) = ?

b. y = .07x + 3.95

c. 8.64 = .07x + 3.95

Solve for x.

Hhb

(a) To find the charge for talking on the phone for 50 minutes, we need to calculate the base cost and the additional cost based on the number of minutes.

First, we calculate the base cost: $3.95 per month.
Next, we calculate the additional cost: $0.07 per minute.

For 50 minutes, the base cost remains the same ($3.95), and we add the cost for the additional minutes.

Additional cost = $0.07 per minute * 50 minutes = $3.50

The total charge is the sum of the base cost and the additional cost:

Total charge = Base cost + Additional cost = $3.95 + $3.50 = $7.45

Therefore, the charge for talking for 50 minutes is $7.45.

(b) To write an equation in slope-intercept form, we need to understand that the monthly cost C depends on the number of minutes used x.

The base cost is $3.95. This represents the y-intercept in slope-intercept form.

The additional cost per minute is $0.07. This represents the slope in slope-intercept form.

So, the equation in slope-intercept form is:

C = 0.07x + 3.95

(c) To find out how much time the person spent talking on the phone if the charge for one month amounts to $8.64, we can rearrange the equation from part (b).

C = 0.07x + 3.95

We substitute the given monthly charge C ($8.64) into the equation and solve for x.

$8.64 = 0.07x + 3.95

Subtracting 3.95 from both sides:

$8.64 - $3.95 = 0.07x

$4.69 = 0.07x

Dividing both sides by 0.07:

$4.69 / 0.07 = x

x ≈ 67

Therefore, the person spent approximately 67 minutes talking on the phone.