The school used to pay an average monthly water fee of 2,549 yuan. After installing the water saving valve. In the first three months of this year, the water bill was 7,137 yuan. After installing the water-saving valve, how much is the average monthly saving in water bills?
学校以前平均每月交水费2549元．装上节水阀后．今年前3个月交水费7137元，装上节水阀后平均每月节约水费多少元？
<gadget id="calculator">7_137 / 3</gadget>
<output>2_379</output>

<gadget id="calculator">2_549 - 2_379</gadget>
<output>170</output>

<result>170</result>