The only thing you need to use if you want to finish Vehicles 3 is your mouse. You have to analyze the situation and start clicking on the right cars to make them move and click on them again if you want them to stop. You will have to stop criminals, put out fires, and help ambulances get to the hospital. This is a puzzle game and you will most likely have to hit the restart button a few times before you finally get it right. In some scenarios, you will have to push vehicles off the stage and then park your car in a designated spot. This means that you need to time your actions carefully and make sure that your vehicle won't slip off the map. The more you play, the easier it will be for you to get used to the challenges. You can skip a couple of levels if they are too difficult, but you will have to go back and finish them if you want to complete the game.
Vehicles 3 is a very well made mind game and it will keep you busy for a while. If you focus on each task, you will eventually find the solution.