you need to find common denominators. 15 . so you have to multiply the 5 from 2/5 by three and the 2 by three to get -6/15. then multiply the four from 4/3 by 5 to get 20 and the 3 by five to get 15, so 20/15. adding a negative is like substracting so 20/15 - 6/15 . 20-6= 14. so its 14/15