Chemistry
posted by Sean P. .
The element europium exists in nature as two isotopes: 151^Eu has a mass of 150.9196 amu, and 153^Eu has a mass of 152.9209 amu. The average atomic mass of europium is 151.96 amu. Calculate the relative abundance of the two europium isotopes.

x = fraction abundance 151 Eu
1x = fraction abundance Eu153.
150.9196(x) + 152.9209(1x) = 151.96.
Solve for x.
You may convert the fractions to percentages by multiplying each by 100. 
thank you Dr Bob!

I don't get it. :'( omg

Ahhhhh it's so confusing...

Uhm........