Question

how can you determine whether a system has no solution by using the substition method?

Answer 1

The number(s) is a solution if when you substitute the number into the equation, the left hand side will equal the right hand side of the equation. If the left hand side does't equal the right hand side then the number(s) substituted in are not solutions.

Answer 2

If your result is unique, x = 4, y = 5, then there is one solution only.
If your result it trivial and maybe a little silly, 0 = 0 or 4 = 4, then there are many solutions.
If your result if false and incorrect, 0 = 12 or 14 = 3/2, then there is no solution.