On a coordinate grid, the coordinates of vertices p and q for polygon pqrs are p(3, 2) and q(−3, 2). what is the length of side pq of the polygon?

The length of the side is the distance between the two points.  The distance between two points is:

d^2=(x2-x1)^2+(y2-y1)^2, so in this case:

d^2=(-3-3)^2+(2-2)^2

d^2=(-6)^2+0^2

d^2=36

d=√36

d=6 units.

Note we could have just observed that the y-coordinate did not change and know that the distance between the two points or the length of the sides was just the change in x:  3--3=6 units.