Answer: Choice D) There are many solutions (infinitely many)
Here are some solutions
(x,y) = (0,-1)
(x,y) = (1,6)
(x,y) = (2,13)
To generate a solution, you plug in any x value you want. For instance, if you plug in x = 2, you get,
y = 7*x - 1
y = 7*2 - 1
y = 14 - 1
y = 13
The values x = 2 and y = 13 pair up to form the solution (x,y) = (2,13)
There are no restrictions on what you can pick for x, so x can be any real number. That's why there are infinitely many solutions. All of the solutions are on the line y = 7x-1