A street light is mounted at the top of a 15ft tall pole. A man 6 ft tall walks away from the pole with a speed of 5ft/s along a straight path. How fast is the tip of this shadow moving when he is 40 ft from the pole

moving shadow-s3-9-7.png

altho there is a triangle in this problem it looks also looks like a ratio problem
thus the equation

$\displaystyle \frac{15}{6} = \frac{x+y}{y}$ or $\displaystyle 2x=3y$

however didn't know how to set this up as a related rate solution
thanks for help

also, how do you insert am image so that you don't have to click the link to see it?