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Natural numbers are closed under division: false.
A set is closed under a certain operation if the results of that operation are always inside that set.
So, if natural numbers were closed under division, the division of two natural numbers would always be a natural number.
You have plenty of counterexamples, to pick one you may divide any odd number by 2: 5/2 is not a natural number.
Negative numbers are closed under addition: true.
Let be two positive numbers. So,
are two negative numbers. Their sum is
And since is positive, we deduce that
is negative, so the sum of two negative numbers is still negative.
Prime numbers are closed under subtraction: false.
This would mean that the subtraction of two primes is also a prime. Again, there are many counterexamples: 7 is prime and so is 3, but their difference 7-3 is 4, which is not prime.
The probability of three independent events happening one after the other is the multiplication of the probability of the single events.
The probability of spinning an odd number is 5/10=1/2, because there are 5 odd numbers (1,3,5,7 and 9) out of the 10 numbers from 1 to 10.
The probability of spinning a number less than 4 is 3/10, because there are 3 numbers (1,2 and 3) that are less than 4 out of the 10 numbers from 1 to 10.
The probability of spinning a 7 is 1/10, because you only have one good outcome out of 10.
So, the probability of winning the game is