The mass ratio of A and B is 5:4, if A gives B 22.5 kg; then their mass ratio is 5:7. How many kilograms does A weigh?
甲、乙的质量比是5：4，如果甲给乙22.5千克；则他们的质量比是5：7．甲原来有多少千克．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">(5/9) - (5/12)</gadget>
<output>5/36 = around 0.138889</output>

<gadget id="calculator">22.5 / (5/36)</gadget>
<output>162</output>

<gadget id="calculator">162 * (5/9)</gadget>
<output>90</output>

<result>90</result>