If a field is 360 feet long and 160 feet wide, using 8 pounds of fertilizer per 1,000 square feet how many bags used to complete the job

First of all, you will need to find the square footage of the field
that is 360*160 
57,600
8 pounds of fertilizer covers 1,000 square feet
(I suppose each bag is 8 pounds)
to see how many square feet each bag covers 1,000/8 
each bag covers 125 square feet
to see how many bags you need, you divide the square footage of the field by how many square feet each bag covers
57,600 / 125
that is 460.8 pounds of fertilizer
460.8 / 50 is 9.216 bags of fertilizer

Hope this helps :)

The last table represents a linear function.