Answer: [-1.8, 3]
Don't forget the square brackets.
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Work Shown:
[tex]|5x-3| \le 12\\\\-12 \le 5x-3 \le 12\\\\-12+3 \le 5x-3+3 \le 12+3 \ \text{ ... see note 1}\\\\-9 \le 5x \le 15\\\\-9\div 5 \le 5x\div 5 \le 15\div 5 \ \text{ ... see note 2}\\\\-1.8 \le x \le 3\\\\[/tex]
note 1: I added 3 to all sides to undo the "-3" in the middle.
note 2: I divided all sides by 5 to go from 5x to x (ie it undoes the multiplication on x).
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From there, we convert from compound inequality notation to interval notation.
Something in the form [tex]a \le x \le b[/tex] converts to the interval notation [a,b]
The square brackets say to include the endpoint.
So [tex]-1.8 \le x \le 3[/tex] converts to the final answer of [-1.8, 3]
x is any real number between -1.8 and 3, including both endpoints.
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It appears you had the right idea. You just needed to convert -9/5 to -1.8, and you also needed to surround everything with square brackets.
If your teacher wanted the answer in fraction form, then you would say [-9/5, 3]
