Since both of the equations are given in a slope-intercept form, we can graph them in a coordinate plane.
The solution to the system is where the two lines intersect.
Therefore, the solution is
In part A, the solution is only determined by the value of because there is no other variable involved. In part B, we have two variables which both have to satisfy the two equations in order to be a solution. This is the difference, that the solution to a system of linear equations is always given as a point.