The school replaced 42 sets of single desks and chairs. Each table is 55 yuan, and each chair is 35 yuan. How much does it cost to buy these desks and chairs?
学校更换了42套单人课桌椅．每张桌子55元，每把椅子35元，购买这些课桌椅要多少元钱？
<gadget id="calculator">55 + 35</gadget>
<output>90</output>

<gadget id="calculator">90 * 42</gadget>
<output>3_780</output>

<result>3_780</result>