A little Physics help from a newbie...

I am stuck on the following problems:

1.) One student, using unit analysis, says that the equation V=√2ax is dimensionally correct. Another says it isn't. With whom do you agree, and why?

2.) A student has a car that gets, on average, 25.0 mi/gal of gasoline. She plans to spend a year in Europe and take the car with her. a- What should she expect the car's average gas mileage to be in kilometers per liter? b- During the year there, she drove 6,000 km. Assuming that gas costs $5.00/gal in Europe, how much did she spend on fuel? (Approximate to the nearest dollar.)

3.) Approximately 118 miles wide and 307 miles long and averaging 279 feet in depth, Lake Michigan is the second-largest Great Lake by volume. Estimate its volume of water in m³.