Give the masses of the three most abundant cl2o molecules

Chlorine has the following % abundance and mass:  

Cl-35 = 75.76 %, 34.9688 amu

Cl-37 = 24.24 %, 36.9659 amu

Oxygen has the following % abundance and mass:  

O-16 = 99.757 %, 15.9949 amu

O-17 = 0.038 %, 16.9991 amu

O-18 = 0.205 %, 17.9991 amu

Based in the % abundance O-16 is the most abundant oxygen isotope and Cl-35 is the most abundant chlorine isotope

So the most abundant molecule of Cl2O and their respective mass are as follows:  

1) Cl-35, Cl-35, O-16

Mass = 34.9688 amu + 34.9688 amu + 15.9949 amu = 85.9325 amu

2) Cl-35, Cl-37, O-16

Mass = 34.9688 amu + 36.9659 amu + 15.9949 amu = 87.9296 amu

3) Cl-37, Cl-37, O-16

Mass = 36.9659 amu + 36.9659 amu + 15.9949 amu = 89.9267 amu