If it's not what You are looking for type in the equation solver your own equation and let us solve it.
21=2d
We move all terms to the left:
21-(2d)=0
We move all terms containing d to the left, all other terms to the right
-2d=-21
d=-21/-2
d=10+1/2
| 31=v+18 | | 15×13=n | | 23=11s | | 6x-2)+(72)=(11x-9) | | 14=d+d | | 33=3q+18 | | 2+5(x+9)=-18 | | –9+2u=1 | | 18x+36=9 | | E^(5x)=14 | | E^5^x=14 | | -20-10k=19-8k-5 | | 8f+15=9f | | 2-3n=9+5n-9n | | -p-10=-3p+10 | | 8-8+8x8=10 | | -7r+9.9=34.9 | | R=-r+2 | | 7g-10=-10-6g | | 1+6t=–5 | | (2/3)x+60000=x | | 19+5y=14 | | 29+177=x | | -10-9t-6t=-14t-17 | | -18z+14=2-2z-14z | | 2.94-5.2h=-5.5h | | -17q=-11-16q | | -14+5r=16+15r | | (12x+4)+(4x+5)=180 | | x-3/8=96 | | 19.7r+17.92=18.1r | | 4(x+1)^4=2500 |