Pls help

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).

In which figure is de bc ? a. figure 1 b. figure 2 c. figure 3 d. figure 4

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?