Final answer:
Tequila must contain at least 51% blue agave according to Mexican law, and while the finest are 100% blue agave, mixtos can be made with a minimum of 51% blue agave.
Step-by-step explanation:
Tequila must be made from at least 51% blue agave. According to Mexican law, for a spirit to be considered tequila, it must be produced in certain regions of Mexico and must be made from at least this percentage of the blue agave plant (Agave tequilana).
The finest tequilas are made from 100% blue agave, but mixtos can have as low as 51% and use other sugars to complete the fermentation process.