Xiao Ming buys a computer anti-virus software, which is 30 yuan cheaper than before after selling it with a 25% discount. So how much did Xiao Ming actually spend on the anti-virus software?
小明购买一种电脑杀毒软件，打七五折销售后比原来便宜了30元，那么小明实际上花了多少钱购买的杀毒软件？
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 / (1/4)</gadget>
<output>120</output>

<gadget id="calculator">120 - 30</gadget>
<output>90</output>

<result>90</result>