A solution to a system of equations are where the two lines cross over each other.
System A the graph shows one line which means the two lines are on top of each other. This means any point on the lines are a solution so there are infinite number of solutions.
System B, the lines cross at one point is there is only one solution which is at (-3,2)
System C the two lines are parallel to each other and never cross so there are no solutions.