Puzzle a Day!

$6

Easy peasy.

A man agrees to work for $9per day. However, if he doesn't turn up at work on any day he will be penalised $6 per day.
At the end of thirty days, the workman is owed nothing.
How many days did he work?

2 + 5/0.5

I'm not sure how to even approach that one, except by trial and error. Can't figure out Mark's answer

Maybe Mark is setting another puzzle?

I reached the answer, but like JJB, by trial and error. Never been good at algebra.

I didn't use algebra to solve it - not knowingly anyway!!

I got the same answer as Mark, but I think I went about it a different way. I didn't find it difficult to come up with an equation to describe the situation, but I really struggled to then solve that equation for x because I'm so rusty! In the end, I had to plug numbers into my equation as I just couldn't solve it any other way! I suspect I may have made it more difficult for myself than I needed to.

Here's my working, if anyone is interested/wants to point out where I went wrong:

We were looking for number of days worked, so I called that x
Pay for days worked = 9x
Days not worked = 30 - x
Pay deducted = 6(30 - x)
So 9x - 6(30 - x) = 0
Solve for x
9x = 6(30 - x) - I added 6(30 - x) to both sides
9x/(30-x) = 6 - I divided both sides by 30-x
Then I tied myself in knots and couldn't remember how to get any further!
I knew x had to be a number between 1 - 30, so I then plugged numbers in and used how close they were to giving me 6 in that equation to work out how far off I was.

I'm impressed Pros

If he works 2 and then has a rest for 3, he gets nothing for 5 days.
There are 6 periods of 5 days in 30 so he must work 5 x 2 days =12