With the information provided, we can begin with the equation:
y=35x + b
With x = number of hours, y = total cost, b = fixed amount that is charged for residential work
We know that after 6 hours, $270 was charged:
$270 = $35(6) + b
Solve for b:
b = $270 - $210 = $60
The fixed amount that is charged for residential work is $60. So now we can rewrite the equation as:
y = 35x + 60