Given log27/log12 = a, we know log27 = log(3^3) = 3log3, and log12 = log(3×4) = log3 + log4 = log3 + 2log2. We need log16/log6 = log(2^4)/log(2×3) = 4log2/(log2+log3). Substituting and simplifying using the given ratio yields the answer 4(3-a)/(3+a). This requires logarithmic properties and algebraic manipulation.