^--------- to, too, or two (but not tutu) ;)
When you say a solution is a point like (0,7) you're probably talking about the intersection of two graphs. Then that point can be substituted into the equation of either graph and the result will be a true statement.
If you are working with straight lines that have linear equations then:
a. if the lines intersect in one point then that is the only solution to the system of equations (the two describing the two lines);
b. if the equations describe the same graphed line (they're just algebraic manipulations of each other), then there are an infinite number of solutions: every point on the line; and
c. if the lines are parallel (same slope but different y-intercepts) then there are no solutions because there are no intersections.