I don't get this question

If the graphs of the linear equations in a system are parallel, what does that mean about the possible solution(s) of the system? a. there are infinitely many solutions. b. there is no solution. c. there is exactly one solution. d. the lines in a system cannot be parallel.

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

If i have 20$ and i gave 5$ away how much i got