原逗早式=2/凯运5÷（-12/山孙雀5）-8/21×（-7/4）-0.5×2÷8=2/5×(-5/12)+8/21×7/4-1/8=-1/6+2/3-1/8=1/2-1/8=3/8
2/5÷（-2 2/5）-8/21×（陆饥-1 3/4）-0.5×2÷8=﹣2/5×5/12﹢8/21×7/4﹣1/2×2×1/8=﹣1/6+2/3﹣毕态1/8=﹙手悉源﹣4+16-3﹚/24=3/8
