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How do you graph linear equation x+y=4

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

7. the area of the playing surface at the olympic stadium in beijing isof a hectare. what area will it occupy on a plan drawn to a scaleof 1: 500?