okay so i would do this with a logarithm.
5^(2x) = 28
take the log of both sides
log5^(2x) = log28 and because of this log rule: logA^n = nlogA
(2x)log5= log28
then divide by log5 on both sides
2x = log28 / log5
and divide by 2
x = (log28 / log5) /2
this can be found with a calculator:
x= about 1.03521...
round that to whatever the question says to