Răspuns:
a=[(26-2)/9+(123-12)/90]:26/1000+19/100:1/100
a=(¹⁰⁾24/9+111/90):26/1000+19/100·100/1
a=(240/90+111/90)·1000/26+19
a=351/90·1000/26+19
a=351000:2340+19
a=150+19
a=169=13·13=13²→ a este p.p
