How can you find it out? [Relative Formula Mass]

In the Periodic Table, Find the elements in the Compound and add them up together. If the Element is like O2, just multiply the Relative mass by 2 to get both atoms Relative Mass If it has brackets in, Just see what elements are in, find the Relative mass and see the number outside the bracket. If its a small 3, then multiply it your Relative Mass by 3.