-3k + 4x - 6k - 7x
Since the variables are not all alike, we will seperate them into two equations based on the variables.
-3k + 6k
4x - 7x
Now find the answers to the equations.
-3k + 6k = 3k
4x - 7x = -3x
Since these answers are unlike variables, the answer to the problem is 3k - (-3x).
Hope this helps!