做对一道得4分,错一道扣2分,若小军做了全部的题,共得36分,那么他做对了多少题

问题描述:

做对一道得4分,错一道扣2分,若小军做了全部的题,共得36分,那么他做对了多少题

设做对了X道题,则4X-2(15-X)=36,解出X=11