Parallels line have the same slope, when an equation is in the form y= mx + b, m is the slope. In this problem slope = - 2
Now with the slope what is missing is the y-intercept, the problem says that the line contains the point (-2, 5), replacing that point in the equation you can solve it to find the y-intercept
The answer is 40 feet long because in the question it asked how long is each rod and each rod is 5 feet and they have 8 rods so you would have to multiply 5 and 8 and you would get 40