Ewa: This is not a system of equations; it's just ONE equation. You can't
"solve" it. However, you could make a table of x and y values that would enable you to graph this relationship. Example: If x=0, y-7=4, or y=11.
Thus, (0, 11) is a point on the graph of this relationship.
Are you sure there wasn't a second equation? If you have a second equation, then the chances are you could solve the system of equations.