The fourth and fifth grade students collected tree species, and the fourth grade collected 13.5 kg, which was 2.8 kg less than the fifth grade. How many kilograms of tree species were collected in the fourth and fifth grades?
四、五年级同学采集树种，四年级采集了13.5千克，比五年级少采集2.8千克．四、五年级一共采集树种多少千克？
<gadget id="calculator">13.5 + 2.8 + 13.5</gadget>
<output>29.8</output>

<result>29.8</result>