2^{x-6} = 7^{2x}
log 2^{x-6} = log 7^{2x}
(x - 6)(log 2) = 2x(log 7)
(x)(log 2) - 6(log 2) = 2x(log 7)
-6(log 2) = 2x(log 7) - xlog 2
-6(log2) = x[2log 7 - log 2]
(-6 log 2) / (2log 7 - log 2] = x