The table below gives the data that is needed to calculate the average atomic mass of element b. isotope atomic mass (amu) relative abundance (%) b-10 10.01 19.91 b-11 11.01 80.09 based on these data, what is the average atomic mass of element b? 10.01 10.51 10.81 11.01

From the table below;
Element B has two isotopes;  One with a mass of 10.01 and a relative abundance of 19,91, while the other has a mass of 11.01 and a relative abundance of 80.09. 
The average atomic mass = (10.01 × 19.91) + (11.01 × 80.09) 
                                         = 1.99 + 8.817 = 10.81
Therefore; the average atomic mass is 10.81.

The average atomic mass = (10.01 × 19.91) + (11.01 × 80.09) 
                                         = 1.99 + 8.817 = 10.81
Therefore; the average atomic mass is 10.81.