Math Help - simple algebra

1. simple algebra

I gota email this 2 the teacher by midnight (it's due in friday) and this website we use like tracks it and will email to the teacher who didn't send it in on time.

I don't even know what you call this question! It's one of those 'Im thinking of a number'

It goes like this:

I am thinking of a number

I multiply it by 11 and subtract 99

I get the same answer if I multiply by 6 and subtract 9

What is my number?

It is just one question, but please im not one of those idiots who just want the answer, if you could explain to me (if anyone out there would take the time) you could use different numbers or whatever, I just want to know the theory!

I would really apreciate a reply, thanks.

Wowplayer1.

2. Originally Posted by Wowplayer1
I gota email this 2 the teacher by midnight (it's due in friday) and this website we use like tracks it and will email to the teacher who didn't send it in on time.

I don't even know what you call this question! It's one of those 'Im thinking of a number'

It goes like this:

I am thinking of a number

I multiply it by 11 and subtract 99

I get the same answer if I multiply by 6 and subtract 9

What is my number?

It is just one question, but please im not one of those idiots who just want the answer, if you could explain to me (if anyone out there would take the time) you could use different numbers or whatever, I just want to know the theory!

I would really apreciate a reply, thanks.

Wowplayer1.
Let the number be $x$, then you are told that $11x-99=6x-9$

RonL

3. So..

11x-99 = 6x-9

11x-99-6x = +6x-6x-9

5x-99=-9

-99-9=-108

5x=-108

-108/5 = -21.6

Huh? THat dont work, what did I do wrong? :S

4. Can someone tell me where I went wrong in my equation? I looked at it for about 20 minutes now can't see where the mistake was.

5. 11x - 99 = 6x - 9

5x = 90

x = 18

6. Cheers =]