what identifies whether the given operation is closed or not closed with respect to each set of numbers.

a. closed
b. not closed

positive integers are under subtraction.

rational numbers are under multiplication.

negative real numbers are under division.

irrational numbers are under addition.

1st is not closed.

2nd is closed

3rd is not closed

4th is closed

Step-by-step explanation:

for the first question it would be the second answer for the second question it would be the third answer and for the third question it would be the first answer

step-by-step explanation:

a) 0.25x times 3. (could be wrong on equation.)

b) 2.25 pound of dark chocolate. (can i eat all the chocolate? plz? anyway, again, could be wrong, but i hope im right. all the chocolate together should be 5.25 pounds)

have a good day!