Open the brackets using the Subjunctive Mood.
If I (to be) an invisible man, I (to have a lot of fun.
If I (to become) a doctor, I (to treat) people for free.
John wishes he (to prepare) better for his exam. He got a bad mark.
If I had a car, I (to travel) all over the country.
I wish I (to be) a mountaineer.