In this video the tutor shows how to add/subtract to solve equations. He says that when we are trying to solve simple equations we need to perform the same operation on both the sides of the equation i.e. if we are adding something on one side of the equation we need to add the same thing on the other side of the equation too. Similarly for the subtraction too. He says that by doing this we still maintain the equality of the equation. He shows how to do this with an example. This video gives an introduction of how to solve simple equation by adding or subtraction from the equation.