If we know that 128 is 74% of something, we can write it like this:
74%x=128.
If we take the percent away (percent means by hundred in latin, 1%=1/100), we'll have
74/100 *x=128
//let's multiply both sides by 100, that way we can get rid of the ugly "/100 because 100/100 = 1, and we can ignore 1 in multiplications
100*74/100 *x = 128 *100// let's simplify the left side: 100/100=1
74*x=128*100// let's calculate the right side now
74*x=12800// now we have to divide both sides by 74
x=12800/74
if we divde this, we have: 172 + 72/74. (why? see below)
We can simplify the fraction by division by 2: 172 36/37
00172
_______
12800:74
-74
___
540
- 518
-------
220
148
_________
72
