A long distance telephone company advertised the rates of 5 minutes for 85¢ and 10 minutes for $1.10.

Use a linear equation to find the cost of a 25 minute phone call.

Let x represent the number of minutes and y the cost. Then

y - 0.85 = (1.10 - 0.85) / (10 - 5) (x - 5)

y - 0.85 = 0.25/5 (x - 5) = 1/20 (x - 5) = 1/20 x - 1/4

y = 0.05x - 0.25 + 0.85 = 0.05x + 0.6

y = 0.05x + 0.6

The cost of 25 minutes = 0.05 (25) + 0.6 = 1.25 + 0.6 = $1.85