Question 1204585

The order is PEMDAS: 
Parentheses, 
Exponents, 
Multiplication, 
Division (from left to right), 
Addition 
Subtraction (from left to right)


you are given:

{{{6 + 42/2  -  15 = 12}}}


here you have no Parentheses, 
Exponents, 
Multiplication,


but you have division, so do that first

{{{6 + 21  -  15 = 12}}}

now you can add and subtract

{{{27  -  15 = 12}}}

{{{12 = 12}}} proven that statement is true