I seemed to have forgot the formula for how to solve such a question so what I did was take my trust calculator, place the number he'd start with each year, multiply it by 0.2 or the 20%, and subtract that from the number he started with to get how many hairs he would start with in the next year. Then rinse-repeat until I got to 10 years.
Example:
1st year would be 1546 - (1546 x 0.2) = 1546 - 309.2 = 1236.8 hairs to start the 2nd year.
At the end of year 10, my calculation had Mr. Jones left with 166.000486 or ≈166 hairs left on his head. I'd suggest Mr. Jones invested in a women's razor; I've heard their blades are better for shaving yourself bald.