0.3X=45
x=45÷0.3
x=150
验算 0.3x150=45
2-4分之1X=3
1/4x=2-3
1/4x=-1
x=-4
验算
2-1/4x-4=2+1=3
5X+4=0
5x=-4
x=-4/5
验算
5x-4/5+4=-4+4=0