2x-6 = 72x
log 2x-6 = log 72x
(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