What is b for this question

How can we find the measure of an exterior angle if we know the measurement of an interior angle

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).

Tom drove 206 miles in 3.9 hours. estimate his average speed.