PLZ HELP

Here is one     9999 - 4360 = 5639

Can give explanation?

difference means subtract.

So you want   

5639 =  one 4 digit number -  another 4 digit number 

If you rearrange this you get

   5639 +  4 digit number = another 4 digit number

 well any small 4 digit number will work for the first one and you can do the addition to get the second number