Como se obtiene el resultado de la operación (2/3) (9/5) (5/4)

The decibel level of sound is 50 db greater on a busy street than in a quiet room where the intensity of sound is watt/m2. the level of sound in the quiet room is db, and the intensity of sound in the busy street is watt/m2. use the formula , where is the sound level in decibels, i is the intensity of sound, and is the smallest sound intensity that can be heard by the human ear (roughly equal to watts/m2).

Ineed i been stuck on this question since yesterday

How many zeros does this polynomial function, y=(x-8)(x+3)^2