Answer:
All answers other than {7, 11, 15, 19}
Step-by-step explanation:
If we have a Set A, it is a subset of Set B if every element in A is also in B. Set A is a proper subset of Set B if it is a subset of Set B but not equal to Set B.
Using the above information, we know that the proper subset of {7, 11, 15, 19} cannot be itself, so we can rule out the second option.
All of the other options are sets where every element of that set is also an element of {7, 11, 15, 19}. The 3rd option is an empty set, which is a proper subset of any set other than itself, so it is a proper subset of {7, 11, 15, 19}.
Therefore, all of the options except for {7, 11, 15, 19} are valid.
Let's let x be the number of t-shirts.
So the first company charges $43 plus $9 per shirt. For x shirts, the cost is the base fee plus 9 times x, or

.
The second company charges a $58 fee plus $8 per shift. The cost is

.
Now, we want to find which fee is less when we are buying 20 shirts. We plug in 20 for x.
The first company charges

.
The second company charges

.
The costs are VERY close, but the second company ultimately charges
less.
Answer:
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Dont understand can u use a pic