Difficult math question?

[Jingoid]

I've just been text messaged this equation by my brother and don't know why as he knows I flunked math so I need a little help.

3 < 2k + 1 < 21
4 < 2 + 2q <= 5 (2q is = to or less than 5)
-3 <= 5r + 2 < 17
-1 < 2 + 1/2s < 7

[scotman]

So what is the question?

[factor-fiction]

3<2k+1<21
Subtract 1 from each of the three expressions:
2<2k<20
Divide each expression by 2:
1<k<10
So k is more than one and less than 10

Do them all in the same way. Take care when multiplying by negatives though.

[Jingoid]

Now that's what I'm talking about! Respect factor 30!

[factor-fiction]

-1 < 2 + (1/2)s < 7
Multiply throughout by 2
-2<4+s<14
Subtract 4:
-6<s<10

[Jingoid]

Okay I will txt him!

[factor-fiction]

I'll leave you or him to try the others.
If you can't do it but can show me you've made a reasonable attempt I'll come back and do the other two.
If you want you can break each one down into 2 parts:
e.g.3 < 2k + 1 < 21 becomes: 3<2k +1 (or 2k+1>3) and 2k+1<21