Simple maths formula - help needed!

I wonder if anyone with a better mathematical brain than mine can come up with a simple formula for this?…

I have 2 attributes (as percentages):
1) Poisoned - Real attribute (value can be between 0-100): 0= no poison, 100= max poison
2) Tolerance - Real attribute (value can be between 0-100): 0= no tolerence, 100 = max tolerence

From these I need a formula to calculate a 3rd Real Atrribute named ‘Health’ (also a percentage: 0 - no health, 100 full health)

So as an example:
If Poisoned = 50, Tolerence = 100, then Health Should = 100.
If Poisoned = 50, Tolerence = 0, then Health Should = 50.
If Poisoned = 50, Tolerence = 50, then Health Should = 75 (I think) etc etc.

Seems simple enough, but I’m struggling!

Thanks if anyone can help!!