6-8号）6 6) (21 - 1,25) : 2,5 ;

To calculate the expression \( (21 - 1.25) : 2.5 \), we will first perform the subtraction and then divide the result.

1. Subtraction: \[ 21 - 1.25 = 19.75 \]

2. Division: \[ 19.75 : 2.5 = \frac{19.75}{2.5} \]

Now we perform the division:

\[ \frac{19.75}{2.5} = 7.9 \]

Thus, the result of the expression \( (21 - 1.25) : 2.5 \) is \( 7.9 \).