Question 71926
{{{21/15-3x<0}}}
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Add +3x to both sides and you get:
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{{{ 21/15 < 3x}}}
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Notice that {{{21/15}}} can be factored to {{{(3*7)/(3*5)}}}.  In this the 3 in the numerator
cancels with the 3 in the denominator.  This reduces the {{{21/15}}} to {{{7/5}}}. The inequality
then becomes:
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{{{7/5 < 3x}}}
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Finally, divide both sides of the inequality by 3 to find:
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{{{(7/5)/3 < x}}}
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When the division on the left side is done the result is {{{7/(5*3) = 7/15}}} so the inequality
is then solved as:
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{{{7/15 < x}}}
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This shows that x is any value that is greater than {{{7/15}}}.  In decimal form 7/15 = 0.4666...
so you can mark 0.4666 ... on the number line then show that x lies at anywhere to the right
of that point ... as far as you can go.
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Hope this helps you to understand how to handle inequalities.  For most cases you can
perform math operations just as you would an equation. One exception is that if you multiply
or divide both sides by a negative number, you have to reverse the direction of the inequality
sign.  In this problem we did not have to multiply or divide BOTH sides by the same negative
number.  Therefore, we didn't have to reverse the inequality direction.  But in some
problems you will have to in order to solve for +x.