If it's not what You are looking for type in the equation solver your own equation and let us solve it.
x in (-oo:+oo)
(3+9)/4 = (x+8)/8+21 // - (x+8)/8+21
(3+9)/4-((x+8)/8)-21 = 0
(-1*(x+8))/8-21+3 = 0
(-1*(x+8))/8+(3*8)/8+(-21*8)/8 = 0
3*8-1*(x+8)-21*8 = 0
16-x-168 = 0
-x-152 = 0
(-x-152)/8 = 0
(-x-152)/8 = 0 // * 8
-x-152 = 0
-x-152 = 0 // + 152
-x = 152 // * -1
x = -152
x = -152
| 2y+3x=y+1 | | 4(2i-3)=20 | | 4x-7/5=6x-5/13 | | 7c*4c= | | 4x-7/5-6x-5/13 | | 13=6x-10 | | 15x-8=10x-33 | | -5.8x=-1.16 | | 37b+45=-3b | | 5(9-2(-4x-7))=40x+115 | | (482)(5.1)/14.4 | | 4x-36y=-32 | | 0.7/5.67= | | Y-40=-6(X-20) | | 9(x-2)/3=6(x+3)/12 | | 0.07(7t+9)=0.49(t-2)+1.61 | | x=3y+15-2x | | 50x^2-98y^2=0 | | 4(x-1)-9=6x-2(4+x) | | 18/13.32 | | 4(p+2)=3(p-6)+p+26 | | x/5+3=x/7+5 | | 6(p+3)=5(p-2)+p+28 | | 10y^2-31y-14=0 | | 2(ln)x+(ln)x^2=3 | | -1.4X=0.056 | | yq+kx=t | | 9(2n+3)=9(7n+8)+8 | | 5(n+7)+1=9 | | kx+qy=t | | 0.3x-1.9=0.2 | | 12-3x=-6x+9 |