The question is asking you to find the value of x, x represents a number. Therefore, 7x means 7 times a number- this the number we are trying to find out. The first step is to get all the numbers containing an x on one side and the numbers on there own on the other side. To move -20 over you would do the opposite function by adding 20. You would also do this for the +3x by taking away 3x. Now you have your terms separated. As 7 and 3 both contain an x you can minus 3x from 7x, the x stays there as you do not know what this equals yet. You can then add 4 and 20. This gives you 4x=24. This tells you that a number times by 4 equals 24. The number of times 4 goes into 24 is the value of x.