36% of what number is 18? show your work

Let 'x' represent the percent of 18.
Let '100' represent the whole 36.

Set up a proportion:
x/18 = 100/36
You cross multiply and get:
36x = 1800
Now divide both sides by 36:
36x/36 = 1800/36
you get:
50

However, if the workers do outside of what's normally expected, go ahead and tip.