How many levels are in the game? You would take that number and multiply it by 0.72 to find 72% of it.
To solve this, create an equation that follows 45% of a value is 18. This would look like x*.45=18. Now, solve for x, x*.45=18, divide by .45, x=18/.45=40, making your value 40. To check, plug in your value to the equation 40*.45=18 and see if it stays true.
That would first be a conversion factor is a number used to change one set of units to another, by multiplying or dividing. when a conversion is necessasry