solve to x?

Solve for x:
y = 3^x

y = 3^x is equivalent to 3^x = y:
3^x = y

Take the logarithm base 3 of both sides:
Answer: | x = (log(y))/(log(3))  for y > 0

To solve when the unknown is an exponent, find the log (either base ten or base e) of both sides:

y = 3^x

log(y)  =  log(3^x)

log(y)  =  xlog(3)                          <since exponents become multipliers>

log(y) / log(3)  =  x                       <divide both sides by log(3)>

You can use either log or ln; if you used ln, your answer is:  ln(y) / ln(3)  =  x