What is the value of the expression below when z=7 ?

3z−3

Ihave a 69 and an 82. the 69 is worth 40% of my grade and the 82 is worth 15%. can someone tell me my current average grade.

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).

If 3x+8=3x+8 is it one solution or no solution