[x+2分之x+1]+[x+7分之x+6]=[x+3分之x+2]-[x+6分之x+5]
[x+(x+1)/2]+[x+(x+6)/7]=[x+(x+2)/3]-[x+(x+5)/6]
2x+(x+1)/2+(x+6)/7=(x+2)/3-(x+5)/6
通分
84x+21x+21+6x+36=14x+28-7x-35
移项
（84+21+6-14+7)x=28-35-21-36
x=-64/104
x=-8/13