0.7×1又4/9+2又3/4×(-15)+0.7×5/9+1/4×(-15)
=0.7×1又4/9+0.7×5/9+2又3/4×(-15)+1/4×(-15)
=0.7×(1又4/9+5/9)+(2又3/4+1/4)×(-15)
=0.7×2+3×(-15)
=1.4-45
= -43.6
0.7×1又4/9+2又3/4×(-15)+0.7×5/9+1/4×(-15)
=0.7×1又4/9+0.7×5/9+2又3/4×(-15)+1/4×(-15)
=0.7×(1又4/9+5/9)+(2又3/4+1/4)×(-15)
=0.7×2+3×(-15)
=1.4-45
= -43.6