1试卷共30道,答对1道得3分,答错1道扣1分,全做,共得78分,答对几道?(方程解答)
问题描述:
1试卷共30道,答对1道得3分,答错1道扣1分,全做,共得78分,答对几道?(方程解答)
答
设答对x道,则打错30-x道
则3*x-1*(30-x)=78
求得x=27
答:答对27道.