x×70%=(x-100)×90%0.7x=0.9x-900.2x=90x=90*5=450希望对你有帮助祝你学业进步！(*^__^*)
7x=9(x-100)2x=900x=450我的解法
x×70%=(x-100)×90%0.7x=0.9x-900.9x-0.7x=900.2x=90x=90÷0.2x=450
