A cell phone company has a monthly charge of 10 dollars for unlimited minutes and 15 cents for each text message. These charges can be expressed as 10+.15t, where t represents the number of text messages sent.

I've seen your responses to the incomplete question. Now here is the answer:

The number of extra messages sent was 285.

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The formula to get the total amount spent for the month on messages is;

$10 + $0.1t; where t = the extra messages after the first 1000 sent for the month

Step-by-step explanation:

Let the cost of each additional message be "t"

Since the unit of total monthly cost was in dollars, let's convert the 10cents to dollars.

Since 100 cents = 1 dollars

Therefore 10 cents = 10/100 = $0.1

We can say that the total cost of the remaining text messages sent for the month was 0.1 x t = $0.1t

The cost of first 1000 messages is $10 dollars a month.

Therefore, total amount spent is $10 + 0.1t

Since we were given that he spent a total of $38.5 for that month,

We can say that $10 + $0.1t = $38.5

Subtract $10 from both sides;

$10 - $10 + $0.1t = $38.5 - $10

To give; $0.1t = $28.5

Dividing both sides 0.1, we get;

t = $28.5/$0.1 = 285

So the number of extra messages sent was 285.

The formula to get the total amount spent is;

$10 + $0.1t; where t = the extra messages after the first 1000 sent for the month