I'm really curious to see how other DIY investors and landlords answer this mental addition question versus the general population.

Um, Jim, not gonna lie, weirdest question I have ever seen in a RE forum. :-)

I add 7 then 20. 

I shift 2 from 27 to 48, then add 25 and 50 to get 75. 

I had the 20 to 48 and then I add the 7 to 68 to get 75. 

Hopefully this will shed light as to why I turn into a werewolf during full moons and run around howling looking for value-add real estate deals. 

I also shift 2 to 48 to get 50, then just add 50 and 25.

My mind adds the 4 and the 2 plus the carry over.

I'm in the minority so far, but I add 40 plus 20, then add the 15. I am waiting for the reply of "full on panic!!!!"

Originally posted by @Jill F. :
(40+20) 60+ (8+7) 15 =75

Same for me!

@Jim K. Take 2 from 27 to make the 48 50, then 50 plus 25 is 75 is how I would do in my head, or would do 8 plus 7 is 15, carry the 1, 4 plus 2 plus 1 is 7 - also 75.... quickly do both ways in my head to check my work :)