Media Services charge $30 for a phone and $20/month for its economy plan. The equation c=20t+30 describes the total cost, c, of operating a Media Services phone for t months. The total cost for 7 months of service is? If customer has only $80 available, how many months of service can she receive?

c = 20(7) + 30 = ?

80 = 20t + 30 = ?

To find the total cost for 7 months of service, you can substitute the value of t into the equation c = 20t + 30.

For 7 months of service:
c = 20(7) + 30
c = 140 + 30
c = 170

So, the total cost for 7 months of service is $170.

Now, let's calculate how many months of service the customer can receive with only $80 available.

We need to solve the equation 80 = 20t + 30 for t.

First, we subtract 30 from both sides of the equation:
80 - 30 = 20t
50 = 20t

Then, we divide both sides of the equation by 20:
50/20 = t
2.5 = t

The customer can receive service for 2.5 months. However, since we can't have a fraction of a month, the customer can receive service for 2 months.

Therefore, the customer can receive 2 months of service with $80 available.