Dad uses 20% of this month's salary as the fee for Xiao Ming to participate in the interest class, and gives the other 450 yuan bonus and the rest of the salary to his mother for family use, so that the money given to his mother is exactly 90% of his father's salary. How much is Dad's salary this month?
爸爸把本月工资的20%作为小明参加兴趣班的费用，把另外的450元奖金和剩下的工资交给妈妈作为家用，这样给妈妈的钱正好是爸爸工资的90%．爸爸本月的工资有多少元？
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(9/10) - (4/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">450 / (1/10)</gadget>
<output>4_500</output>

<result>4_500</result>