Help me its math . :|

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

Two variables, x and y, vary inversely, and x=12 when y=4. what is the value of y when x=3?

The graph shows the decibel measure for sounds depending on how many times as intense they are as the threshold of sound. noise in a quiet room is 500 times as intense as the threshold of sound. what is the decibel measurement for the quiet room? 20 decibels28 decibels200 decibels280 decibels