Operation sequence: parentheses-multiplication and division-addition and subtraction, and the operations at the same level are calculated from left to right.

Rules for removing brackets: minus sign before brackets, plus sign after brackets, plus sign after brackets.

For example:

( 148- 1 1 1÷37)×5

=( 148-3)×5

= 145×5

=725

47 - (2 1 - 15)×5

=47-6×5

=47-30

= 17

105-5×(48÷3- 1 1)

= 105-5×( 16- 1 1)

= 105-5×5

= 105-25

=80