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Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

What percent of 18 is 24? and plz explain thx.

Robert plans to make a box-and-whisker plot of the following set of data. 27, 14, 46, 38, 32, 18, 21 find the lower quartile, the median, and the upper quartile of the set? lower quartile: 19.5; median: 29.5; upper quartile: 42 lower quartile: 14; median: 27; upper quartile: 46 lower quartile: 18; median: 27; upper quartile: 38 lower quartile: 16; median: 29.5; upper quartile: 42