Consider the reasoning step below: 
To find the percentage of semi-automatic cars, we need to divide the number of semi-automatic cars by the total number of cars and then multiply by 100 to express the result as a percentage.

Step 1: Determine the total number of cars:
There are 20 cars available for rent.

Step 2: Determine the number of automatic cars:
There are 12 automatic cars.

Step 3: Determine the number of manual cars:
There are 4 manual cars.

Step 4: Determine the number of semi-automatic cars:
Since the problem states that 4 of the cars are manual and the rest are semi-automatic, there are no more manual cars to count.

Step 5: Find the percentage of semi-automatic cars:
The total number of cars is 20, and 4 of them are manual, leaving 16 cars that are either automatic or semi-automatic. Out of these 16 cars, 12 are automatic and 4 are semi-automatic. The percentage of semi-automatic cars is (4/16) * 100 = 25%.

Therefore, 25% of the cars available for rent are semi-automatic.

What's wrong?