When to not use order of operations?

Question

I was taking a quiz on evaluation expressions, and one of the questions asked me to evaluate 25-5e+ 3/f when e=4 and f=3. And I used PEMDAS, and multiplied 5(4), which is equal to 20. Then I divided 3/3, which is equal to 1. After that I added 20 + 1, which is equal to 21. And finally, I subtracted 25-21, and I got 4 as my solution, but it said that it was wrong. So, was I not suppose to use order of operations? Can someone please help me out. Sorry for my bad English.  

Answer 1

25 - 5e + 3/f 

 

For e = 4 and f = 3:

 

25 - (5)(4) + 3/3 = 25 - 20 + 1 = 6

 

You can't add the 20 + 1 because it's really 25 + (-20) + 1.  So you should have added -20 + 1 = -19.  Then add -19 to 25 to get 6.  It's easier to remember to just do the additions and subtractions left to right, then you won't have problems.

Answer 2

You first two operation were correct

25 - 20 + 1

addition/subtraction from left to right!

5 + 1

6