a student buys a bag of granola snack mix that has a mass of 0.522 kg

. The student eats 0.216 kg of the snack mix.

To find out how much snack mix is left, we can subtract the amount eaten from the total mass of the bag:

0.522 kg - 0.216 kg = 0.306 kg

So, the student has 0.306 kg of snack mix left in the bag.