3 6 per 15 - 9 per 20

Semoga bisa membantu ya:)

3  [tex] \frac{6}{15} [/tex] - [tex] \frac{9}{20} [/tex] = 2 [tex] \frac{84 - 27}{60} [/tex]
    =2 57/ 60 = 2 19/20

semoga membantu