When you have 7x+5=5x+17, you try to get the variables on one side and the constants on the other. Subtract 5x from the right and from the left: 2x+5=17. Next, subtract 5 from the left and from the right: 2x=12. The last step is to get rid of the coefficient of x and to do that divide it by the coefficient(in this case divide both sides by 2). After dividing 2x and 12 by 2 you get x=6.
