小中学校範囲の算数・数学の問題のスレ　Part 61

前>>204訂正。
>>160
9y/(0.282x+0.09y)=9・991/(0.282・929+0.09・991)
=8919/(261.978+89.19)
=8919000/351168
=1114875/43896
=25.39……(%)