The solution of two equations/lines is their intersect point. Therefore, there can only be one intersection point/solution, because these lines are neither parallel or identical. In the graph you can see that they intersect at (x,y)=(2,3) which is your solution and option b or d as one of them seems to be mistyped :)
@question2 y=kx+b
both your equations share the same k=-2: y=-2x+3 y=-2x-1
therefore these lines are parallel and don't have any intersection as they are always at different y values (the b)
