Question

the average atomic mass of a sample of element X is 23.04u what are the percentage of isotopes ²³X₁₁ and ²⁴X₁₁ in the sample ?

Answer 1

$$\begin{gathered} Averageatomicmass=\frac{x_1{M}_1+x_2{M}_2}{x_1+x_2} \\ {x}_1+x_2=100 \\ {x}_2=100-x_1 \\ 23.04=\frac{23\times x_1+24\times (100-x_1)}{100} \\ 2304=23x_1+2400-24x_1 \\ {x}_1=2400-2304 \\ =96\% \\ {x}_2=100-x_1=100-96=4\% \end{gathered}$$
So
x₁ = 96 %
x₂ = 4 %