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Actually, I am pretty sure the left one is correct:

The problem here is the programming in the Calculator. Classic vs Math Print mode
Read more here if interested:
https://en.wikipedia.org/wiki/Order_of_operations

For the actual solving of this problem gotta know:

PEMDAS

Parentheses - Perform Operation Inside Parentheses
Exponent- N/A here
Multiplication/Division - From Left to Right; So where 2(3) does = 6; you have to divide first before multiplying. The way you did it actually has a historical precedent that before 1917 would have been correct (watch here, you need sound for the end, as he explains why):

Addition/Subtraction - N/A as this was done in the parentheses

So steps:

  1. 6/2(2+1) = 6/2(3)
  2. 6/2(3) = 6/2x3
  3. 6/2x3 = 3x3
  4. 3x3 = 9

9 is the correct answer!

Math is a wonderful thing:
Substitute X for (2+1) and Y as the unknown
6/2X=Y
Remove 2X from the left side by multiplying both sides by 2X
6= 2XY
Divide both sides by 2
3=XY
Replace 2+1 for X
3=(2+1)*Y
Solve for Parenthesis
3=3Y
Divide both sides by 3
1=Y

Next talk about lies, damn lies and statistics.

You know it