If it's not what You are looking for type in the equation solver your own equation and let us solve it.
k in (-oo:+oo)
21-(2*k) = k/10 // - k/10
21-(2*k)-(k/10) = 0
21-2*k-(k/10) = 0
21-21/10*k = 0 // - 21
-21/10*k = -21 // : -21/10
k = -21/(-21/10)
k = 10
k = 10
| 3x-15=14-2x-6 | | 12(x-2)+7(y+1)=25 | | y=55x+200 | | (-3u+3)x(u^3-1)= | | y=17(4)-28 | | 2(2x+4)=3x+1 | | -4z+24=-3z-6 | | 12x+5=3x+19 | | x+2x+27+x=163 | | -(x-4)=-1 | | -10(x+4)=9 | | -11=17x-28 | | 5(8x+8)-2(2-7x)=12+55x | | 48y-63=37y+55 | | x-1.5y=-3 | | 16=10+3m | | 8y+1=-31 | | 4x^2+18x= | | 7(2+x)=3x+1 | | -6(k-2)-(-7k+1)=3 | | .5x-12=-14 | | 2y-6+4y-8=0 | | (x+2)+(27+x)=163 | | ln(x)-ln(x-1)=ln(x+3)-ln(x+5) | | 7y-(11-4y)=6 | | 43=26+e | | -2a+5a-13+12= | | 8.50t=51 | | 18+3-2y=5y+3y | | y=17(-3)-28 | | -5/3 | | -7x+11=32 |