that's a shitload of lines of math to write out/work in your head. I learned percentages of x as: 6 * 45 / 100 = x (2.7) If you picture both as fractions, you multiply the opposite and then divide by the other number to get the missing one (x). Hopefully Lemmy renders this well...
| 6 | x |
| 100 | 45 |
The way I learned it was multiply diagonally and then divide by whatever is opposite diagonally to x.