Intermediate BIDMAS with simpler brackets, addition and subtraction

Note: This intermediate BIDMAS option includes both harder brackets and negative numbers in the 'running total,' unlike the basic practice option. It is suggested you become comfortable with the basic version and then progress to intermediate. If you want to practice full bidmas with complex brackets, powers, multiple and divide, please choose the 'advanced' BIDMAS option - this is not under the mental maths section but under the paper maths options.

BIDMAS refers to the order of operations in an expression.
The most important operators are on the left of BIDMAS, starting with B, and the least on the right-hand side, ending with AS.

BIDMAS stands for:

B Brackets
I Indices ( powers )
D Division
M Multiplication
A Addition
S Subtraction

Note: primary schools in the UK tend to call this BODMAS Where the O stands for 'other.'
In the USA, it is known as PEMDAS Where P = Parentheses and E = exponents.
'Parentheses' is just the correct name for these kinds of brackets: ( and ) .
Exponents means the same thing as powers.

Thus:

Brackets - most important - work these out first.
Indices - next most important - work these out next.
Multiplication & Subtraction - these are equal importance, so work them out as you see them working left to right.
Addition & Subtraction - these are equal importance, so work them out as you see them working left to right.

Examples

• 10 - 4 + 2     : Do 10 - 4 first, making 6. Next do 6 + 2 to give a final answer of 8.
  
  
• 10 - ( 4 + 2 )    : Do the brackets first, so 4 + 2 = 6, so the expression becomes 10 - (6).
  Lastly do 10 - 6 giving a final answer of 4. In this way you can see the brackets can make a big difference.
  
  
• (3 + 2) - ( 10 - 9 )    : Do the first brackets : 3 + 2 = 5, so the expression becomes: (5) - ( 10 - 9 )
  Next do the second bracket: 10 - 9 = 1, so the expression becomes (5) - (1) giving a final answer of 4.
  Note you don't have to wrap a single number in brackets like this: (5) as it just means "5," , but it is sometimes
  easier to keep track of things like this.
  
  
• 3 + 2 - 10 - 9    : This is the same as the above but without brackets. It's just addition and
  subtraction, so work left to right: 3 + 2 = 5 . Next do 5 - 10 which comes to -5. Lastly do -5 -9 which equals -14.
  Notice again what a big difference brackets can make.
  
  
• 9 - ( 7 - ( 6 - 2 ))    : This time we have a bracket inside a bracket. In this case, you do the
  inside brackets first, left to right : 6 - 2 makes 4, so it all becomes: 9 - ( 7 - (4))
  Next do 7 - 4 which gives 3, so the expression becomes: 9 - 3. This gives a final answer of 6.

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Difficulty Levels - typical questions :

1:  ( 2 - ( 2 + 1 + ( 9 + 2 - 3 ) ) + 5 ) + 8
2:  ( 16 - 6 - ( 3 - ( 2 + 2 - 10 ) + 11 ) ) - ( 6 - 8 + 18 )
3:  ( 16 + 12 - 10 ) + ( ( 27 - 3 - 29 ) + ( 17 + 27 + 16 ) + ( 2 - 17 + 15 ) ) + 28