If the minuend increases by 2.9 and the subtrahend decreases by 1.7, how much does their difference increase?
如果被减数增加2.9，减数减少1.7，那么它们的差增加多少．
<gadget id="calculator">2.9 + 1.7</gadget>
<output>4.6</output>

<result>4.6</result>