5x+7=2x+21,0.13x+12=0.8x-1,3（x-7)-(x-4)=15,解方程,急,

5x+7=2x+21,0.13x+12=0.8x-1,3（x-7)-(x-4)=15,解方程,急, 解方程 x+2/x+1+x+8/x+7=x+6/x+5+x+4/x+3 解方程1/(x+x﹚+1/(x+3x+2﹚+1/(x+5x+6﹚+1/(x+7x+12﹚=4/21得 方程(x-1/x-2)-(x-3/x-4)=(x-2/x-3)-(x-4/x-5)解为x=7/2,(1/x-7)-(1/ 解方程(x-2)/(x-3)-(x-3)/(x-4)=(x-5)/(x-6)-(x-6)/(x-7) 解方程(x+1/x+2)-(x+2/x+3)=(x+5/x+6)-(x+6/x+7) 解方程：x+2/x+1-x+3/x+2=x+6/x+5-x+7/x+6 解方程:(x+3)/(x+2)-(x+5)/(x+4)=(x+7)/(x+6)-(x+9)/(x+8) 解方程x/(x-2)=2x/(x-3)+(1-x)/(x-5x+6) 解方程:2(X-3)(X+5)=X平方+(X+2)(X-2)+(X+7) 解方程(x²-x+4)x-(x-1)(x²+2)=x+7 解方程 x(2x-4)+3x(x-1)=5x(x-3)+8