Express in logarithmic form:

y=27(1/3)^2x

ln y = ln 27 + 2x*ln(1/3)

ln y = ln 27 - 2x*ln 3
ln 27 - ln y = 2x ln 3
ln (27/y) = 2x * ln 3
2x = ln(27/y)/ln(3) = log3(27/y)
x = 1/2 log3(27/y)