Question 621678
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Hi,
For example: collecting Like terms: 1-9   or 1 + (-9) on a number Line...
 Starting at 1 and going 9 units to the{{{highlight(left)}}}, one is on  {{{highlight(-8)}}}       
{{{number_line( 600, -10, 10,  1,-8 )}}}
Likewise: {{{x - 9x = highlight(-8x)}}} when collecting Like Terms