6×7+3×5+5×4-4×5-2×7+3×9+9×2-3×6-7=
42+15+20-20-14-27+18-18-7=
57+20-20-14-27+18-18-7=
57-14-27+18-18-7=
43-27+18-18-7=
16+18-18-7=
34-18-7=
16-7=9
