4g mixture of NaCl & NaBr contains 30% Na in the total mixture.Calculate the percentage composition?

a, b = amt of (NaCl) and (NaBr)

(NaCl) = mass of (NaCl) = 23+35
(NaBr) = mass of (NaBr) = 23+70


a(NaCl)+b(NaBr)=4

(a+b)(Na)=4(30%)

solve for a, b