-14<=4x-9<=-4
When you see an inequality, and most other equations, with one variable, your first job is usually to add, subtract, multiply, or divide, to get the variable on its own, isolated from the numbers. Just remember to do the same thing to both sides.
This one has three sides, but the same principle applies. You could break it down into two, if it makes it eastier to see:
-14<=4x-9 and
4x-9<=-4
In this case, there are two things you need to do to get x on its own, out of the 4x-9 expression:
1. Add 9 to all sides, to get rid of the 9, and then
2. Divide all sides by 4, so that you're looking at x on its own.
I'll start you off:
-14<=4x-9<=-4
-14+9 <= 4x-9+9 <=-4+9
Work that out, and then you'll be left with
something <= 4x <= something
Divide everything by 4 and you're done.