Idon't know what the symbol means or what to do.

Step-by-step explanation:

That weird symbol means "element".  In our case, the elements of the domain (the x-values) are -15, -6, -1.  Which tells us that we are going to sub each one of the numbers into the equation and solve it for the corresponding y value.  That in turn gives us the coordinate point.  The equation is

x + y = 6

Subbing in first -15 for x:

-15 + y = 6 and

y = 6 + 15 so

y = 21 and the coordinate point is (-15, 21).

Subbing in -6 for x:

-6 + y = 6 and

y = 6 + 6 so

y = 12 and the coordinate point is (-6, 12).

Subbing in -1 for x:

-1 + y = 6 and

y = 6 + 1 so

y = 7 and the coordinate point is (-1, 7)

The second choice is the one you want.

Just remember that x is the domain and any elements in the domain go in for x.

Also remember that y is the range and any elements in the range go in for y