Since the tank is ¾ full, then you need to fill it with ¼ tank.  If there are 20 gallons in a tank, then ¼ of a tank is 20 / 4 = 5 gallons.  If the cost is 1.20 per gallon, then it will cost 5 * 1.2 = $6 to fill it up.
 

Back to Answer Sheet