In order to solve for k you always want to try and isolate the variable (trying to get only k on one side of the equal sign). You can start of by distributing 6 into the numbers in the parenthesis. So 6 times 2k is 12k and 6 times 8 is 48. So in reality, you now have 12k+48= -48. Then you can subtract 48 from the left side to cancel it out. Note: you would not add 48 to cancel out the -48 on the right because you need a number on both sides of the equal sign. So once you subtract -48 from one side you must do it to the other so -48-48 is -96. Now you have 12k=-96. All you have to do now is cancel out the 12k but dividing since it is the inverse of multiplying. Divide 12 from both sides and -96 divided by 12 is -8.
So your answer is k=-8