Answer:
%C₁ = %C₂ = 50%
Explanation:
Set up simultaneous equations to solve for two unknowns,
let f₁ and f₂ = fractional abundances of C₁ and C₂ respectively.
Then f₁ + f₂ = 1.00 and
34.97f₁ + 36.97f₂ = Wt. Avg. Atomic Mass (amu) = (34.97 + 36.97)/2 = 35.97amu
Solve equation 1 for f₂ = 1 - f₁ and substitute into equation 2
=> 34.97f₁ + 36.97(1 - f₁) = 35.97
=> 34.97f₁ + 36.97 - 36.97f₁ = 35.97
=> 2f₁ = 1
=> f₁ = 1/2 = 0.50 => 50% abundance for C₁
=> f₂ = 1 - 0.50 = 0.50 => 50% abundance for C₂
