2/5k-3/5+1/10k. You can only add together like terms, which means only the terms with k after it can be United. You need to make 2/5 be over 10 so you do 5 times 2, which means you also must do the numerator by 2 as well, getting 4/10. 4/10k-1/10k is 3/10, making the answer 3/10k-3/5.