BODMAS:- the correct sequence in which the operation are to be executed.

‘B’ – bracket, ‘o’- of , ‘D’- division , ‘M’- multiplication, ‘A’- addition , ‘B’- substraction.

Virnaculum(or bar)- when an expression contains virnaculum before, applying the BODMAS rule, we simplify the expression under the virnaculum sign –

[b-(b-a-b)]

[b-(b-a+b)]

[b-2b+a]