Solution: Align the two addend units, and then add the numbers in the same counting unit respectively. If the addition result exceeds 10, the high bit of 1 will be removed, and the addition of the high bit needs to accumulate the low bit of 1.

Problem solving process:

Step 1: 2+ 1=3

Step 2: 8+9=7 to the high position, 1.

Step 3: 7+4+ 1=2 to the high position, 1.

According to the above calculation steps, the comprehensive calculation result is 1273.

Checking calculation: 1273-49 1=782

Extended data # Check calculation result: align the units of the subtrahend and the minuend, and then subtract them from 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 subtrahend is less than the minuend, add a negative sign to the final result of two numbers. Fractional subtraction can refer to the integer subtraction step;

Problem solving process:

Step 1: 3- 1=2

Step 2: 17-9=8 high borrowing 1.

Step 3: 12-4- 1=7 Borrow from high position 1.

Step 4: 1-0- 1=0.

According to the above calculation steps, the comprehensive calculation result is 782.

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