A store sells hardcover books for $8 and paperback books for $5. You buy 9 books, represented by the equation x+y=9, where x is the number of hardcover books and y is the number of paperback books. The equation 8x+5y=51 represents the total cost. How many of each type of book did you buy?

Just tell me how to set up the equation.

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.

What is the measure of one interior angle of a pentagon