Parallel planes never touch
Yes you are doing it correctly.
$12.00 + $3.00x <= $24.00
$12.00 + $3.00x - $12.00 <= $24.00 - $12.00
$3.00x <= $12.00
$3.00x/$3.00 <= $12.00/$3.00
x <= 4
The number line representation will be an arrow with a shaded round head pointing to the left from tne number 4.
