Three of the methods and examples below each have an elegant/straight forward alternative technique that cuts away the complexity of awkward conversions that are optional.
For example, 75%−23%{\displaystyle 75%-23%} is the same as 75100−23100{\displaystyle {\frac {75}{100}}-{\frac {23}{100}}}.
For example, since 75−23=52{\displaystyle 75-23=52}, you know that 75100−23100=52100{\displaystyle {\frac {75}{100}}-{\frac {23}{100}}={\frac {52}{100}}}.
For example, 52100{\displaystyle {\frac {52}{100}}} converted to a percent is 52%{\displaystyle 52%}.
For example, 68%−9. 5%{\displaystyle 68%-9. 5%} is the same as . 68−. 095{\displaystyle . 68-. 095} (or 68 hundredths minus 95 thousandths).
For example:0. 680−0. 0950. 585{\displaystyle {\begin{array}{r}0. 680\-0. 095\\hline \0. 585\end{array}}}
For example, to convert 0. 585{\displaystyle 0. 585} to a percent, move the decimal place two places to the right: 58. 5{\displaystyle 58. 5}. So, 68%−9. 5%=58. 5%{\displaystyle 68%-9. 5%=58. 5%}
68. 0%−9. 5%58. 5%{\displaystyle {\begin{array}{r}68. 0%\-9. 5%\\hline \58. 5%\end{array}}}
For example, you might need to subtract 123. 688% from 50%. Since 123. 688 is larger than 50, your answer will be negative.
For example:50. 000%−123. 688%{\displaystyle {\begin{aligned}50. 000%\-123. 688%\\hline \end{aligned}}} becomes123. 688%−50. 000%{\displaystyle {\begin{aligned}123. 688%\-50. 000%\\hline \end{aligned}}}
For example: 123. 688%−50. 000%73. 688%{\displaystyle {\begin{aligned}123. 688%\-50. 000%\\hline \73. 688%\end{aligned}}}
Thus, 50%−123. 688%=−73. 688%{\displaystyle 50%-123. 688%=-73. 688%}.
50. 000%−123. 688%−73. 688%{\displaystyle {\begin{array}{r}50. 000%\-123. 688%\\hline \-73. 688%\end{array}}}
For example, 30%{\displaystyle 30%} converted to a decimal is 0. 30{\displaystyle 0. 30}.
For example, 120×0. 3036. 00{\displaystyle {\begin{array}{r}120\\times 0. 30\\hline \36. 00\end{array}}}
For example, 120−36=84{\displaystyle 120-36=84}. So, 120−30%=84{\displaystyle 120-30%=84}.
100%−30%{\displaystyle 100%-30%} = 70%{\displaystyle 70%} The price will be 70% of the original price, so simply find 70% of $120 – using the decimal equivalent 70% = 0. 70 multiply the original price – to get the discounted price. For example, $120×0. 70$84. 00{\displaystyle {\begin{array}{r}$120\\times 0. 70\\hline \$84. 00\end{array}}}
