Every now and then I come across a “puzzle” on Facebook that asks to solve some simple math problem. Claiming something like “only smart ones know” or “only for genius”.

Last “puzzle” looked like this:

```
3-3x6+2=??
```

And there was 331K of comments all with answers or discussions.

I hope readers of my blog are all maths-literate and know rules of multiplication and addition. And I hope nobody is going to argue here that the answer is -13.

But out of curiosity I looked through comments and I was horrified how many people got this wrong. And insisting that their incorrect solutions is right. Some comments got my attention:

The first guy gives the explanation how this should be calculated. And then somebody comes and challenges saying that addition should be done before subtraction. Now I should insert an gif-image saying “My mind is blown”.

Now here we have somebody referring to “rules of bodmas”.

I did not know what these rules are, so had to look up. Turned out that I knew the rules, I just did not know that “BODMAS” is the yet another name for these rules. So this person clearly understood that you should do your multiplication first, but then struggled to do additions correctly.

Another common answer was 2. That is what you get if you use your calculator and go “three minus three multiply by six add two”. You’ll get 2. And many people did:

Some people clearly never paid attention in their maths class:

You get the picture. List of incorrect answers goes on and on. There are a lot of `-13`

answers, but they go roughly for 20-30% of all the answers. I wish I could extract data from all the comments and get some statistics out.

Honestly, after looking on a mass of different answers I started question my sanity and if I got the answer correctly, so I even wrote this down on a paper and re-done the “calculations”.

You may ask what I’m getting at? Yes, people have no idea about maths and it is hard. And programming is harder. You need to know these rules – operations ordering and that `-7+4`

is `-3`

, not `-11`

. And that in some programming languages you can get `a=null`

always equals to `true`

because we are assigning `null`

to variable `a`

and operation is always successful. So learn your maths before trying to program.