Formula field clarification

Formula field clarification

Hi

I have been on a bunch of tutorials to develop a new formula but just cant make it happen, let me explain

Field A, B and C

I would like the "formula field" to displays "X" everytime "Field A" and "Field B" meet specific criteria
Example: 
Field A= Food
Field B= 50%
Formula field = Healthy food

Can you guys help me with the formula for this, I would really appreciate it!!

Bests