What does if mean for a system of linear equations to be "one-to-one"?
Every range (y-coordinates) corresponds to only one part of the domain (x-coordinates)
x | y
1 | 2
2 | 3
3 | 4
In this table, each y-coordinate is only used once, so it is a one to one function.
To test if a function is one to one you can use the vertical/horizontal line test. This is when you draw a vertical or a horizontal line on the graph if the vertical/horizontal line only touches the graphed line once then it is a one to one function.