What are kilometers and explain in words.

A kilometer is a unit of length or distance.  It's defined as
the length of 1,000 meters.

To perhaps give you a better feel for it . . .

         1 kilometer = about 1,094 yards

         1 kilometer = about  0.621 mile

         1 mile  =  about  1.61 kilometers

Almost every place in the world outside of the USA posts their
distances and speed limits on their road signs in kilometers
instead of miles.

The equation is y=17(7)+600 and it equals 717