16 3/21- 1 5/21

is it 5 2/21?

well, 16 - 1 is certainly not 5

16 3/21 is just short for 16 + 3/21
you can't subtract 5/21 from 3/21, so let's make that
16 3/21 = 15 24/21
Now you have
(15 + 24/21) - (1 + 5/21)
and now, because addition is associative and commutative, that's
= (15-1) + (24/21 - 5/21)
= 14 19/21

It occurs to me that maybe you meant 15 2/21, not 5 2/21

If so, it indicates that you did the 16-1 right, but subtracted the */21 in the wrong direction.
The answer could have been 15 - 2/21
In other words, 14 19/21

No.

Change 16 2/21 to 15 24/21
Now do the subtraction.

To subtract mixed numbers, you need to follow these steps:

Step 1: Convert the mixed numbers into improper fractions.
Step 2: Find the common denominator.
Step 3: Subtract the fractions.
Step 4: Simplify the resulting fraction, if necessary.
Step 5: Convert the resulting fraction back to a mixed number, if desired.

Let's apply these steps to the problem you presented:

Step 1: Convert the mixed numbers into improper fractions.
16 3/21 can be written as (16 * 21 + 3)/21 = 339/21
1 5/21 can be written as (1 * 21 + 5)/21 = 26/21

Step 2: Find the common denominator.
Since both fractions have the same denominator (21), we can proceed to the next step.

Step 3: Subtract the fractions.
339/21 - 26/21 = (339 - 26)/21 = 313/21

Step 4: Simplify the resulting fraction, if necessary.
In this case, the resulting fraction 313/21 is already in its simplest form.

Step 5: Convert the resulting fraction back to a mixed number, if desired.
To convert the improper fraction 313/21 back to a mixed number, you divide the numerator by the denominator:
313 รท 21 = 14 remainder 19

So, 313/21 can be expressed as 14 19/21.

Therefore, the correct answer to the subtraction 16 3/21 - 1 5/21 is 14 19/21, not 5 2/21.