The school needs to set up the venue for the activity, so they bought the same number of red balls and green balls in the store. Children's Day discount, both kinds of balls are sold for 1 yuan and 2 balls, and the school spent 168 yuan less. How many balls did the school buy in total?
学校要布置活动场地，到商店买了相同数量的红球和绿球，红球原价2元3个，绿球原价5元7个．六一节优惠，两种球都按1元2个卖，结果学校少花了168元钱．学校一共买了多少个球？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">(2/3) - (1/2)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) - (1/2)</gadget>
<output>3/14 = around 0.214286</output>

<gadget id="calculator">(1/6) + (3/14)</gadget>
<output>8/21 = around 0.380952</output>

<gadget id="calculator">168 / (8/21)</gadget>
<output>441</output>

<gadget id="calculator">441 * 2</gadget>
<output>882</output>

<result>882</result>