We assume that the number 43 is 100% because it's the output value of the task. Also that x is the value that we are looking for. So you write down
100% = 43
Next x% equals 18 of the output value. So you write it down as x% = 18
Now we have two simple equations which is 100%=43 and x%=18
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:
100%/x%=43/18
Now we just have to solve the simple equation. Solution for 18 is what percent of 43?
(100/x)*x=(43/18)*x - we multiply both sides of the equation by x
100=2.38888888889*x - we divide both sides of the equation by (2.38888888889) to get x
100/2.38888888889=x
41.86=x
x=41.86
Now we have: 18 is 41.86% of 43
