A car uses 20 gallons of gas to travel 400 miles. Mr. Montero's car has 8 gallons in it. How many more gallons of gas does he need to travel 600 miles, back and forth?
Mr. Montero is traveling a total distance of 600 miles + 600 miles = 
<gadget id="calculator">600+600</gadget>
<output>1_200</output>
1200 miles.
There are 1200 miles / 400 miles = 
<gadget id="calculator">1200/400</gadget>
<output>3</output>
3 sets of 400 miles in 1200 miles.
So Mr. Montero needs 20 gallons/set x 3 sets = 
<gadget id="calculator">20*3</gadget>
<output>60</output>
60 gallons in all.
Since his car has 8 gallons already, then he needs to add 60 gallons - 8 gallons = 
<gadget id="calculator">60-8</gadget>
<output>52</output>
52 gallons more.

<result>52</result>