# Question #3beef

Mar 27, 2016

We start by subtracting $3$ from both sides:

#### Explanation:

$21 - 3 < \cancel{3} - \cancel{3} + 9 x$
$18 < 9 x$
Now divide by $9$:
$2 < x \to x > 2$

You may add and subtract on both sides.
Only if you multiply or divide by a negative number, the $>$ sign changes into a $<$ sign and vice versa. We didn't do that.