Could someone help me understand this ?

Step-by-step explanation:

It looks like they might want you to solve this.

That is find a value of k that satisfies the equation.

We can first cross-multiply ( if  a        c

                                                  --  =   --    then    a*d = b*c  ).

                                                  b        d

So k * 17 = 6 * -6

17k = -36

Divide both sides by 17:

k = -36/17.