1. Suppose A = { 1, 3, 5, 7, 9, 11 , 13} and B = {2, 3, 5, 7, 11, 13}. Find the value of A U B .  2. suppose c: {prime numbers less than or equal to 20}. find n(C)

3. Suppose A = { 2, 3, 4, 5, 6, 7, 9, 12} , B = {2, 12, x, 9} and B is a subset of A. What possible values could x have?

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Problem 1

Explanation:

The notation A U B means we're applying a union between A and B. This will form a larger set in which items from A or B are thrown into A U B. Think of "union" as in getting married, and person A's stuff is combined with person B's stuff to form a larger set. Any duplicates are tossed. It's often helpful to sort from smallest to largest.

Problem 2

Explanation:

Set C is defined as the set of prime numbers less than or equal to 20. The roster form is C = {2,3,5,7,11,13,17,19} which basically lists every item that fits the description earlier. Note how the value 1 is not prime, so it's not in the set C.

From here, we simply count out the values in set C to find there are 8 values. Therefore, n(C) = 8.

Problem 3

Explanation:

Let's consider a real world example of set vs subset. Consider the set of all animals and consider the subset of all dogs. Let's say

A = all animals

B = all dogs

We can see that set A is clearly larger than B. Also, any member of set B is also in set A, but not the other way around. In other words, if something is a dog, then they are also an animal. However, this doesn't work the other way around. For instance, we could have a cat in set A that wouldn't be in set B.

Let's return to the problem at hand. Since B is a subset of A, this must mean everything in B = {2,12,x,9} is found in set A. Sure enough, the 2, 12 and 9 are all in set A. The x must also be a value in set A so we could have

x = 3

x = 4

x = 5

x = 6

x = 7

as our possible answers. I'm not listing x = 2, x = 9 or x = 12 as they have been taken care of. I'm assuming that your teacher wants {2,12,x,9} to list unique items (ie it's after the duplicates are tossed out).

this was already solved by me with a different person. if you look it up in the search bar at the top of the page, you will get the answer.

step-by-step explanation:

answer: the answer is 35%