orenken6121 orenken6121 14-09-2022 Chemistry contestada element x has 3 isotopes. the 1st isotope has a mass of 23.98 amu and 78.70%. the 2nd isotope has mass of 24.99 amu and 10.13% and the 3rd isotope has mass of 25.98 and is 11.17%. what is their average mass?