The sum of (5/7) and 1.3 of a number is equal to 2.5, find this number. (solution by equation)
一个数的(5/7)与1.3的和等于2.5，求这个数．(用方程解)
<gadget id="calculator">2.5 - 1.3</gadget>
<output>1.2</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1.2 / (5/7)</gadget>
<output>1.68</output>

<result>1.68</result>