A box of toothpaste is 5.8 yuan, which is 1.9 yuan more expensive than a toothbrush. How much does it cost to buy a toothbrush?
一盒牙膏5.8元，比一把牙刷贵1.9元，买一把牙刷需多少元．
<gadget id="calculator">5.8 - 1.9</gadget>
<output>3.9</output>

<result>3.9</result>