Since last time I am talking to Dean at his Calculus, he says.....that is as far as I didn't done a math until 2018, where is Dean I don't know, on that Comet math.

Then 2021, I done once those elaborate math out of my brain.

I never done math, sometimes on Erin's bill, how much is the tip in America? 15 %?

You done that 10 divide, cut in half, added on from 10%.

That is what nick I think he does those thing, he uses his brain or a pen the same thing. There are certain math Australian, some human has a school....on something must be a tradition one of those how to write a math. 

You eating? 3 meals a day, lunch would be 9.50 still in America? Thai it was 7 dollar something.

So you take that one decimal move over, that will 10 %

then you do half, adding up, to that 10 number, that is the exactly the same thing.

0.95+0.47=  1.42

You can just saying double check, that 10% of 10 dollar always =1 dollar tip, you cannot get it wrong, that is 0.9

you add that to 9.5

10% its 0.9, forever never lower than that.... 

You can do 0.9/2 makes easy 0.45 + to that 0.9=1.35

So that is the lazy human getting a cheap tip. I don't do that.