The set consist of numbers 0 and 1 so if we use any combination of those 2 numbers under some operation and get as result one of those 2 numbers that means set is closed under that operation.
for multiplication you get:
0*0 = 0 0* 1 = 0 1 * 1 = 1 so all combinations used and answers are 0 and 1 which means set is closed under multiplication
It isnt for subtraction and addition because: 0-1 = -1
