Answer:
21.78
Step-by-step explanation:
The fraction 4/5 has the decimal value 0.8. The mixed number 25 4/5 is equivalent to the decimal number 25.8.
When you do the subtraction, you may want to add a trailing zero to 25.8 to make the same number of decimal places as 4.02. Then you have ...
25.80 -4.02
and subtraction proceeds in the normal way.
25.80 -4.02 = 21.78
_____
It is useful to memorize the decimal equivalents of fractions with denominators of 10 or less. It is also helpful to note that denominators of 2 and 5 and their multiples can be translated directly to fractions with denominators of 10 or other powers of 10: