In this video he just explained about how to solve an algebra problem. The problem is -7+13x=58. He just solve the problem in simple steps. First you find out the x in this problem. To find out x you just add 7 to each side. Then it will be -7+7+13x=58+7. Then the equation will be 13x=65 because in the left side of the equation -7 canceled by +7 so then the equation is 13x=65. Next you just add the divide by 13 each side of the equation. Then the equation will be 13x/13=65/13. Then 13 divided by 13 is 1, then obviously left side of the equation you will get 1x. Next you just divide 65 by 13. it will 5. So now the equation will be 1x=5 then obviously it will be x=5. If you substitute the x into the first equation will get the correct equation.