a+b=(20×5+9)/20
a+b=109/20
a)a=2intregi 5/16=37/16
37/16+b=109/20
b=109/20-37/16
aducând la același numitor 80
b=(109×4-37×5)/80
b=(436-185)/80
b=235/80
b=47/16
b)a=61/20
61/20+b=109/20
b=(109-61)/20
b=48/20
b=12/5
c)a=(10×4+3)/10
43/10+b=109/20
b=109/20-86/20
b=23/20