To build a road, 4.8 kilometers were built on the first day, which was 0.9 kilometers more than the second day. How many kilometers were built in two days?
修一条路，第一天修了4.8千米，比第二天多修了0.9千米，两天共修了多少千米？
<gadget id="calculator">4.8 - 0.9</gadget>
<output>3.9</output>

<gadget id="calculator">3.9 + 4.8</gadget>
<output>8.7</output>

<result>8.7</result>