-13×三分之二-0.34×七分之二+三分之一×（-13）-七分之五*0.34
=-13×2/3 -0.34×2/7 -13×1/3 -5/7 ×0.34
=-13×(2/3+1/3) -0.34×(2/7+5/7)
=-13×1 -0.34×1
=-13.34
（2×3×4×5）×（二分之一-三分之一-四分之一+五分之一）
=(2×3×4×5)×(1/2-1/3 -1/4 +1/5)
=(2×3×4×5)×(1/2)-(2×3×4×5)×(1/3)-(2×3×4×5)×(1/4)+(2×3×4×5)×(1/5)
=3×4×5-2×4×5-2×3×5+2×3×4
=60-40-30+24
=14
-1.57×(+21.8)+6.28×(-24.7)-3.14×39.7
=-1.57×21.8 +1.57×4×(-24.7) -1.57×2×39.7=-1.57(21.8+4×24.7+2×39.7)
=-1.57×200
=-314