1-(0.7+3x）÷0.8=(0.3x-1)÷0.4-x
1-(0.7+3x)×5/4=(0.3x-1)×5/2-x
1-7/8-15x/4=3x/4-5/2-x
1/8+5/2=3x/4-x+15x/4
14x/4=21/8
x=21/8÷14/4
x=3/4