Final answer:
If two linear equations have the same slope and y-intercept, they represent the same line and therefore have infinitely many solutions.
Step-by-step explanation:
If you are given two linear equations in slope-intercept form where both equations have the same slope and the same y-intercept, then the lines represented by these equations are identical. Therefore, they are superimposed one upon the other on the graph and have infinitely many solutions because every point on one line is also on the other line. This is because in slope-intercept form (y = mx + b), the slope (m) dictates the steepness and direction of the line while the y-intercept (b) dictates where the line crosses the y-axis. When two lines have the same values for both m and b, they are the same line.