Of the 20 available cars for rent, 12 are automatic cars, 4 are manual cars, and the rest are semi-automatic. What percentage of the cars are semi-automatic?
12 + 4 = 
<gadget id="calculator">12+4</gadget>
<output>16</output>
16 cars are either automatic or manual.
So, 20 - 16 = 
<gadget id="calculator">20-16</gadget>
<output>4</output>
4 cars are semi-automatic.
Therefore, the percentage of semi-automatic cars is 4/20 x 100% = 20%.

<result>20</result>