The mean of three

Let the three numbers be a, b and c.

According to the problem, a = 19

And

Or

Which gives 19+b+c = 120

So b+c = 101

Consider b = 100, which gives c = 1 which is not possible because the lowest number allowed is 19.

Consider b = 40 which gives c = 61

Consider b = 71, which gives c = 30

Consider b = 81, which gives c = 20

Among these b = 81 is the highest number.
Therefore, the correct answer is 81.