posted by Sam .
An unknown element Q has two known isotopes: 61Q and 62Q. If the average atomic mass is 61.4 amu, what are the relative percentages of the isotopes?
Let x = fraction of 61Q
Then 1-x = fraction of 62Q
x*61 + (1-x)*62 = 61.4
Solve for x and 1-x, then convert to percent.