Solve, using the substitution method.
y – 3x = 7
21 9x = 3y
a.
there is no solution.
b.
there are an infinite number of solutions.
c.
the solution is (1, 10)
d.
the solution is (28, 0)

Adecibel is a logarithmic unit that can be used to measure the intensity of a sound. the function y = 10logx gives the intensity of a sound in decibels, where x is the ratio of the intensity of the sound to a reference intensity. the reference intensity is generally set at the threshold of hearing. use the graphing utility to graph the decibel function. a whisper has a sound intensity of 30 decibels. use your graph to you complete the following statement. the sound intensity of a whisper is times the reference intensity.