4/5-4/5÷2/3×1/2
=4/5-4/5*3/2*1/2
=4/5(1-3/4)
=4/5*1/4
=1/5
(3/4-3/4×2/5)÷1/5×5
=3/4(1-2/5)*5*5
=3/4*3/5*5*5
=45/4