Answer :

First we have to multiply 2 times 5k and -6 and simplify
-4k+2(5k-6)=-3k-39
-4k+10k-12=-3k-39
-4k+10k-12=-3k-39
6k-12=-3k-39           /+3k
9k-12=-39               /+12
9k=27                    /:9
k=27:9
k=3 - its the answer