Buying 3 footballs and 5 basketballs costs 281 yuan, and buying 3 footballs and 7 basketballs costs 355 yuan. How much would it cost to buy 3 footballs and 6 basketballs?
买3个足球和5个篮球共用281元，买3个足球和7个篮球共用355元．现在要买3个足球和6个篮球，一共要用多少元？
<gadget id="calculator">281 + 355</gadget>
<output>636</output>

<gadget id="calculator">636 / 2</gadget>
<output>318</output>

<result>318</result>