If 1.216g of cobalt metal react with 0.495g of oxygen gas what is empirical formula of the cobalt oxide product

First you divide each mass by the mass number of the element:

Cobalt        1.216 / 59 = 0.02

Oxygen      0.495 / 32 = 0.03

Then the result is divided by the lowest number:

Cobalt        0.02 / 0.02 = 1

Oxygen      0.03 / 0.02 = 1.5

After that you multiply with a number to obtain an integer number:

Cobalt        1 × 2 = 2

Oxygen      1.5 × 2 = 3

The empirical formula of the oxide:  

CoO