A utility company charges $67.65
plus $1.1917 per therm for gas usage in excess of 50 therms. Last winter, one homeowner's bill ranged from a low of
$196.35 to a high of $214.23.
Over what range did gas usage vary (in therms)?
well, for usage over 50 therms, the bill for x therms is
y = 67.65 + 1.1917(x-50)
So, plug in your y values and solve for the x values.