Element X has 3 isotopes - 77, 79, 82. The natural element is 22% 77X, 48% 79X and 30% 82X.?

The procedure for this is simple: take the number of the isotope (77,79,82) times their respective percents. Add the numbers together to get the atomic weight. The formula for this problem is (.22x77)+(.48x79)+(.3x82). once you do the math it calculates to 79.46. Look on the periodic table to see which element has an atomic weight that is similar to that number. Element X can be either bromine (79.90) or selenium (78.96), but it is most likely bromine.