Question

Question #3beef

Answer 1

We start by subtracting `3` from both sides:

Explanation:

`21-3 < cancel3-cancel3+9x`
`18<9x`
Now divide by `9`:
`2 < x -> 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.