Thinking of solving problems: Four arithmetic rules (calculation in sequence, first multiplication and division, then addition and subtraction, first parenthesis, first power), that is, disjoint operation (recursive equation calculation), should be carried out on the premise of this principle.

Problem solving process:

23+ 12- 18

=35- 18

= 17

Extended data->; Vertical calculation-calculation result: align the units of the subtrahend and the minuend, and then subtract them from the numbers in the corresponding counting units respectively. If the subtraction is not enough, you need to borrow 1 from the high position, and then calculate the results in turn. If the subtraction is less than the minuend, the two numbers are exchanged and subtracted, and a negative sign is added to the final result; Fractional subtraction can refer to the integer subtraction step;

Problem solving process:

Step 1: 15-8=7 Borrow from high position 1.

Step 2: 3- 1- 1= 1.

According to the above calculation steps, the comprehensive calculation result is 17.

If in doubt, please ask questions. If satisfied, please adopt them.