k/9-1=12
We move all terms to the left:
k/9-1-(12)=0
We add all the numbers together, and all the variables
k/9-13=0
We multiply all the terms by the denominator
k-13*9=0
We add all the numbers together, and all the variables
k-117=0
We move all terms containing k to the left, all other terms to the right
k=117
