Răspuns:
a+b=45+12 supra 54=67 supra 54
a-b=45-12 supra 54=33 supra 54
a=13/6
a+b=3=>b=3-13/6=>b=5/6
a-b=13/6-5/6=12/6=2
a=7/8
a-b=12=>b=7/8-12=>b=7/8-96/8=>b=-89/8
a+b=7/8-89/8=82/8=41/4
b=13/12
a-b=2/3=>a=2/3+13/12=>a=8/12+13+12=>a=21/12
a+b=21/12+13/12=34/12=17/6
