## Chemistry 9th Edition

The abundance of $^{151}Eu$ is 48.013 %. The abundance of $^{153}Eu$ is 51.986 %.
We may relate the two abundances by $x$, the abundance of $^{151}Eu$ and $(1-x)$, the abundance of $^{153}Eu$. Therefore, we may write the following equation calculating the average atomic mass: $151.96=150.9196*x+152.9209(1-x)$ $151.96=-2.0013x+152.9209$ $x=\frac{152.9209-151.96}{2.0013}$ $x=0.48013$ $(1-x)=0.51986$