3 If is 100%, so we can write it down as =100% 4 We know, that x is 2% of the output value, so we can write it down as x=2% 5 Now we have two simple equations 1) =100% 2) x=2% where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that /x=100%/2% 6