Question 375493
You are off to a good start!  You have written the inverse variation function for intensity (I):
{{{I = k/d^2}}} Now you need to find the value of k, the constant of variation.  You do this by substituting the given values of {{{I = 25}}}W/m^2 and {{{d = 2}}}meters:
{{{25 = k/2^2}}} so that...
{{{k = 100}}} Now the function for intensity looks like:
{{{I = 100/d^2}}} Now you can answer the question posed in the problem:
"How far (d) are you from the transmitter when the intensity (I) is 2.6W/{{{m^2}}}?
Substitute the values into the last equation:
{{{2.6 = 100/d^2}}} Solve for {{{d^2}}}.
{{{d^2 = 100/2.6}}} Take the square root of both sides.
{{{d = 10/sqrt(2.6)}}}meters.
{{{d = 6.2}}}meters. 
Intensity is Watts per square meter or {{{W/m^2}}}