A school organizes a party and uses balloons to decorate the venue. Among them, red balloons account for 15% of the total number of balloons. If there are 210 fewer balloons in other colors, and the total number of red balloons is the same as that of other colors, how many balloons are used to decorate the venue?
某校组织联欢会，用气球布置会场，其中红色气球占气球总数的15%，若其他颜色的气球共减少210个，红色气球与其他颜色气球总数相同，则布置会场共用了多少个气球？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (3/20) - (3/20)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">210 / (7/10)</gadget>
<output>300</output>

<result>300</result>