If the trucker changes the oil every 10,000 miles and he starts the year with a fresh oil change how many times will he change the oil in a year

You would need to know how many miles truckers drive each year. Once you know the mileage you then divide by 10,000 to yield the number of oil changes in a year's time.

One would have to know how many miles the trucker travels in a year. It appears as if that data is not provided. Once that total mileage per year is known, then divide that value by 10,000 to yield the number of oil changes in a year's time.