The school originally had 680 exercise books, but 478 were used and 350 were bought. How many exercise books does the school have now?
学校原来有680本练习本，用去478本，又买来350本．学校现在有多少本练习本？
<gadget id="calculator">680 - 478</gadget>
<output>202</output>

<gadget id="calculator">202 + 350</gadget>
<output>552</output>

<result>552</result>