The right answer is 170 bpm.
The maximum heart rate depends on age and can be estimated by a simple rule, "220 minus age". For example, a 50 year old man will have a MHR of 170.
For women, it is advisable to use the "226 minus age" rule.
This formula is simple, but the least reliable of existing formulas: the standard deviation of the result obtained is about ten.
This data allows the athlete to know how far to push his effort. Most of the time, his sessions take place between 70 and 80% of his MHR, if their goal is to increase his respiratory capacity and the oxygenation of the muscles required (endurance work).