Solve for t in terms of the other variables.
k= 3tm + rs

Step-by-step explanation:

It's like solving any equation, except we have letters instead of numbers .

k = 3tm + rs           {subtract rs from both sides}

k - rs = 3tm            {divide both sides by (3m)}

             {swap sides}

           m≠0    

{m must be ≠0 because  you cannot divide by 0. There is no t for m=0}    

not sure but it may be b, as i said i'm not sure.