Kent multiplies both sides of the equation below by an expression.

k+12/k=8

then he moves all the terms to one side of the equal sign in the resulting equation. which equation must he solve now?

The steps below are presented in order to arrive to the value of k of the given equation. 
First, multiply both sides of the equation by the variable k since the left-hand side of the equation has it in the denominator. This will be,  
            (k + 12/ k)(k) = 8(k)

Then, we simplify,
             k + 12 = 8k
We then, subtract 8k to both sides of the equation,
           k - 8k + 12 = 8k - 8k

Simplifying,
                  -7k + 12 = 0

Then, subtract 12 from both sides of the equation and divide both sides by -7. This will us the final answer of,                  
                     k = 12/7