Wendy's truck has a gas tank that can hold 20 gallons. She also has a car with a gas tank that holds 12 gallons. The truck's tank is half full. The car's tank is 1/3 full. If she fills them both up completely, how many gallons does she add?
The truck tank has 10 gallons in it because 20 x .5 = 
<gadget id="calculator">20*.5</gadget>
<output>10</output>
10.
The car tank has 4 gallons in it because 12 x (1/3) = 
<gadget id="calculator">12*(1/3)</gadget>
<output>4</output>
4.
She needs to add 10 gallons to the truck because 20 - 10 = 
<gadget id="calculator">20-10</gadget>
<output>10</output>
10.
She needs to add 8 gallons to the car because 12 - 4 = 
<gadget id="calculator">12-4</gadget>
<output>8</output>
8.
She needs to add 18 gallons in total because 10 + 8 = 
<gadget id="calculator">10+8</gadget>
<output>18</output>
18.

<result>18</result>