21:(-2 1/3

To solve the expression 21:(-2 1/3, we need to convert the mixed number -2 1/3 to an improper fraction first.

-2 1/3 as an improper fraction is -7/3

Now, to divide 21 by -7/3, we should multiply 21 by the reciprocal of -7/3, which is -3/7:

21 ÷ (-7/3) = 21 * (-3/7) = -9

Therefore, the result of 21:(-2 1/3) is -9.