Solve:

3^x=7
3^2x+1=12
4^x-6=2^3x

x log 3 = log 7

x = log 7/log 3

unclear what is exponent 2 or 2x or 2x+1
use parentheses

I will guess
4^(x-6) = 2^3x
2^2(x-6) = 2^3x
so
2x-12 = 3x