Originally Posted by

**extraordinarymachine** Hi, i need help please on how to set up this question, and how to solve it. Thanks!

The intensity, I, of light, in lumens, passing through the glass of a pair of sunglasses is given by the equation I(x) = $\displaystyle I_{0}(0.8)^x$ , where x is the thickness of the glass, in millimetres, and $\displaystyle I_{0}$ is the intensity of the light entering the glasses. How thick should the glass be so that it will block 25% of the light entering the sunglasses?