简算 12+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10

按计算机吧

12+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10
=3×4+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10
=2×3×4+2×3+4×5+5×6+6×7+7×8+8×9+9×10
=2×3×(4+1)+4×5+5×6+6×7+7×8+8×9+9×10
=6×5+4×5+5×6+6×7+7×8+8×9+9×10
=5×(6+4)+5×6+6×7+7×8+8×9+9×10
=10×(5+9)+5×6+6×7+7×8+8×9
=14×(10+7)+5×6+8×9
=14×17+2×3×(5+12)
=14×17+6×17
=17×(14+6)
=17*20
=340
轮换应用乘法分配率.

12+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10
=12+6+12+20+30+42+56+72+90
=340
或这是：
12+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10
＝12+3(2+4)+5(4+6)+7(6+8)+9(8+10)
=340

12+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10
=3×4+2×3+3×4+4×5+5×6+6×7+7×8+8×9+9×10
=2×3×4+2×3+4×5+5×6+6×7+7×8+8×9+9×10
=2×3×(4+1)+4×5+5×6+6×7+7×8+8×9+9×10
=6×5+4×5+5×6+6×7+7×8+8×9+9×10
=5×(6+4)+5×6+6×7+7×8+8×9+9×10
=10×(5+9)+5×6+6×7+7×8+8×9
=14×(10+7)+5×6+8×9
=14×17+2×3×(5+12)
=14×17+6×17
=17×(14+6)
=17*20
=340