13+x=28.

13+x=28. 5.1x-x=28. 4x+9x=13x X+13%X-28%X=3. x+13%x-28%x=3.4 13x-6.8x+x=46. 13x-15x+x=-3 x*x-10*x=13急 10x+[13-x]+9=10[13-X]+X (13-x)*10+x+27=10x+13-x 2*x*x+2.5x=13 x=? 13x-6.3x+x=46.8 x=多少 x+5.5x=13 (x-10)/(x-11)+(x-16)/(x-17)=(x-12)/(x-13)+(x-14)/(x-15)快,急用 解方程((13x-x^2)/(x+1))(x+(13-x)/(x+1))=42 (13x-x^2)/(x+1)[x+(13-x)/(x+1)]=42 x+x+x+x+y=40 x+y= 13x=y= 1x+2x+3x+4x+5x+6x+7x+8x+9x+10x+11x+12x+13x+14x+15x=550必须用解方程