Question 115452
Let the number of minutes he could talk be 'x'.

For the first minute the cost is $0.96.

So, for the remaining 'x - 1' minutes the cost is $0.72.

So, the total cost is $0.72(x - 1) + 0.96.

The amount should not exceed $6.

So, the inequality is $0.72(x - 1) + 0.96 < = $6

That is, 0.72x + 0.24 < = $6

That is 72x + 24 < = 600.