Subtract Two 2digit Numbers  Within 100
To subtract two digit numbers, first align the numbers so that place values are lined up.
Subtract ones regroup if needed and then subtract tens.
For example: Let's find the difference of 45 and 16.
Align the numbers and subtract ones. Regroup if needed.
3  15  
4  5  

1  6 
9 
Now, subtract the tens.
3  15  
4  5  

1  6 
2  9 
The difference of 45 and 16 is 29.
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Help
The correct answer is
Remember :
The smallest number is the one that comes first while counting.
Solution :
To arrange the given numbers in order from smallest to greatest, find the smallest number among all the given numbers.
21,27,23
21 is the smallest number.