(1.6*0.8)*0.75 =(3×1.6-2×0.8)*0.75 =3.2*0.75 =3×3.2-2×0.75=9.6-1.5=8.1
△*(4*1)=7 求△
△*(3×4-2×1)=7
△*10=7
3△-2×10=7
3△=27
△=9