What is the value of the expression of -(-4)

Is the orthocenter of a triangle on the inside ?

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).

Which is equivalent to 10/12? options: 10/18 5/6 3/12 9/11