We can estimate the answer before we start to be somewhere between 2 and 3, because 32 = 9 and 33 = 27. But how do we find the answer?
First we take the logarithm of both sides of the given equation:
log 3x = log 12.7
Now, using the 3rd log rule
logb (xn) = n logb x,
we have:
x log 3 = log 12.7
Now divide both sides by log 3:
x = (log 12.7)/(log 3)
= 2.3135
Is it correct? Checking in the original question, we have: 32.3135 = 12.7. Checks okay. Also, our answer is between 2 and 3 as we estimated before.