Another gas that was used to fill balloons was hydrogen. The reason why hydrogen is not used today is because it use to cause many fires when it was used to fill balloons up.
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The periods inside the Periodic Table is B. a horizontal row, and is numbered 1 through 7
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Answer: -9x^2 -31x -36 I hope this helped! ~GalaxyGamingKitty Can I have Brainliest if it is right?