A road construction team builds a road of 1800m in 15 days, and actually builds 20m more than planned every day. How much is the original plan to build roads per day?
一个修路队，15天修路1800m，实际每天比计划多修20m，原计划每天修路多少m．
<gadget id="calculator">1_800 / 15</gadget>
<output>120</output>

<gadget id="calculator">120 - 20</gadget>
<output>100</output>

<result>100</result>