You can reverse the inequality also to bring you to the same answer.
Notice above that we did not do any multiplying or dividing by negative numbers,
hence no reversal was ever needed.
\(\displaystyle 3(3-2x)\ \le\ 15\)
\(\displaystyle 3-2x\ \le\ 5\)
Now, multiply (or divide) both sides by \(\displaystyle -1\) to get the co-efficient of x positive.
However, you can add 2x to both sides to also get the co-efficient of x positive.
Getting the co-efficient of x positive is necessary to find it's boundary.