7/9*(x-0.4)=2/3
x-0.4=2/3÷7/9
x-0.4=6/7
x=6/7-0.4
x=16/35
5/8x+1.8=4.3
5/8x=4.3-1.8
5/8x=2.5
x=2.5÷5/8
x=4