Answer:
10 motorcycles and 30 cars
Step-by-step explanation:
If there are 25 cars and a 5:2 ratio, then 25/5=5, and 5x2=10, then there will be 10 motorcycles.
          5:2
  Divide by 5 | Multiply by 2
If there are 12 motorcycles, then 12/2=6 and 6x5=30. The ratio is reversed because the translation required is reversed.
           2:5
  Divide by 2 | Multiply by 5