SOLUTION: Danny made a mistake in the following problem. In which line was the mistake made? Line 1: 21 + 35 divided by 7 + 6(2) Line 2 : 21 + 5 + 6(2) Line 3: 21 + 11(2) Line 4: 2

The mistake is in the order of operations, called "PEMDAS" or "Please
Excuse My Dear Aunt Sally".

1.  Operations within innermost parentheses
2.  Exponential operations
3.  Multiplication or Division operations as you come to them going left to right.
4.  Addition or Subtraction operations as you come to them going left to right.     


Line 1:  21+35÷7+6(2)

There are two additions, a division and a multiplication to do.
By rule 3 above we must do the division 35÷7 before the
multiplication 6(2) because it comes first going left to right, 
so we replace 35÷7 by 5

Line 2:  21+5+6(2)

 
That was line 2, so that was correct.

The next step should be to do the multiplication 6(2) and replace
the 6(2) by 12 like this:

Line 3:  21+5+12  

But the given Line 3 was 21 + 11(2).  So that was the error. The 5+6
was replaced by 11, but the multiplication 6(2) must be done before
the addition.

So the error was in step 3.  The error was in adding 5+6 when 6(2)
should have been done before the addition.

You will get the wrong answer if you violate "PEMDAS", the order of
operations.

Edwin