Ribosomes make a good target for antibacterial drugs because

Answer;
Ribosomes make a good target for antibacterial drugs because it is the site where protein synthesis takes place. Thus these antibiotics inhibits the process of protein synthesis and thus the bacteria dies.

Explanation;
Bacterial ribosome are organelles inside bacterial cells where protein synthesis takes place. Antibiotics that target bacterial protein synthesis do so by interacting with the bacterial ribosome and inhibiting its function. By inhibiting the process of protein synthesis bacteria will not survive as they wont be able to carry out any survival processes. 

This is what i did 45-5=4040÷4=10so there are 10 white marbles but am not sure is just a question that am not sure