Anita is 5 ft. tall and walks at the rate of 4 ft./sec away from a street light with its lamp 12 feet above ground level. Find an algebraic representation for the length of Anita's shadow as a function of time, t.

Express the distance, D, between the street light's lamp and the tip of Anita's shadow as a function of time, t.

I tried drawing a picture using a triangle, but cannot get it at all. Any ideas?