**Answer:**

(-oo, 1) U (1, 3) U (3, oo)

**Step-by-step explanation:**

We have a line with two arrowheads. The arrow heads show us that the numbers in the set continue forever in the negative direction past -5 and in the positive direction past 5. In this case, the set consists of all real numbers except 1 and 3 since they have open circles.

That means the set is from negative infinity to 1, from 1 to 3, from 3 to positive infinity, but leaving out 1 and 3.

Remember that a regular parentheses symbols, ( and ), do not include the number near them and are used for open circles.

Square brackets, [ and ], do include the number near them and are used for closed circles.

Also, infinity and negative infinity are not numbers, so we always use regular parentheses when dealing with infinity or negative infinity.

We need the union of three sets:

from negative infinity to 1, from 1 to 3, from 3 to positive infinity

Answer: (-oo, 1) U (1, 3) U (3, oo)