Li Hong's weight is 42 kg, Wang Yan's weight is 36 kg, Lin Hai's weight is the sum of Li Hong's and Wang Yan's weight (1/2), what is Lin Hai's weight in kg?
李红的体重是42千克，王艳的体重是36千克，林海的体重是李红、王艳体重总和的(1/2)，林海的体重是多少千克？
<gadget id="calculator">42 + 36</gadget>
<output>78</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">78 * (1/2)</gadget>
<output>39</output>

<result>39</result>