This is exactly like the one with the 'n's that you posted yesterday.
I guess you didn't get enough help on that one to understand it.
7k/8 - 3/4 - 5k/16 = 3/8
3/4 is the same as 6/8.
Add it to each side of the equation:
7k/8 - 5k/16 = 9/8
Multiply each side by 16 :
14k - 5k = 18
Add up the 'k's on the left side:
9k = 18
From this point, you can proceed directly to the numerical value of 'k'
if you need it.
In your question, you said you need help, and I showed you how to
strip the problem down so that the only thing left is ' k = something '.
Giving you the answer is no help. Nobody actually needs the answer.