Brackets    Indices    Division    Multiplication    Addition    Subtraction


BIDMAS is a mnemonic to help us to remember the correct order in which to do calculations.
If we had, say, 7 + 3 x 2 and did the calculation from left to right 7 + 3 = 10.  We then multiply by 2 and the answer is 20
This answer is wrong because we did the calculation in the wrong order. BIDMAS tells us that we must do multiplication before addition.
So, 3 x 2 is 6. We can add the 7 now to get 13. By using BIDMAS we get the correct answer.
Always resolve Brackets first. Then Indices. Division and/or Multiplication next and finally Addition and/or Subtraction.