The current price of a pen is 15.4 yuan, which is 30% lower than the original price. Find the original price of this pen, and what is the formula.
一支钢笔现在售价是15.4元，比原来售价降低了30%，求原来这支钢笔的售价，列式是多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">15.4 / (7/10)</gadget>
<output>22</output>

<result>22</result>