X÷3+3(100-X)=100x÷3+300-3x=100x÷3-3x=-200x-9x=-600-8x=-600x=75祝学习进步,望采纳。不懂得欢迎追问。。
变形X+900-9X=3008X=600X=75
x/3+3(100-x)=100x+9(100-x)=300x-9x+900=300-8x=-600x=75