Here are some excellent videos on solving simultaneous equations:
The first three videos go through solving Simultaneous equations using the Graphical Method. The third one looks at the case where there is NO solution because the lines are parallel.
The next four videos go through the Elimination Method for solving Simultaneous Equations (relating to Ex 4C)
The next two videos look at solving simultaneous equations using the Substitution Method (Ex 4B). It would be good practice to pause the video, solve it yourself, and then play the video to see if you were correct.
Here is an outstanding web page which clearly explains how to solve simultaneous equations and goes through the three methods: graphical, algebraic (substitution and elimination) http://www.mathwarehouse.com/algebra/linear_equation/systems-of-equation/
Here is another page from this great site which explains how to sketch linear inequations on the Cartesian plane and has a really great visual demo: http://www.mathwarehouse.com/algebra/linear_equation/linear-inequality.php
Here is an excellent video on how to graph a linear inequality with two variables