1. Zadatak

Kako je $\frac bc=\frac52$, slijedi da je $b=\frac{5c}2$, pa nakon zamjene u jednakost $\frac ab+\frac ac=\frac{11}{10}$ imamo $$\frac a{\frac{5c}2}+\frac ac=\frac{11}{10},\quad\frac{2a}{5c}+\frac ac=\frac{11}{10},\quad\frac{2a}{5c}+\frac{5a}{5c}=\frac{11}{10},\quad\frac{7a}{5c}=\frac{11}{10},\quad\frac75\cdot\frac ac=\frac{11}{10},$$ odakle je $\frac ac=\frac{11}{10}\cdot\frac57=\frac{11}{14}$. Sada je $\frac ab+\frac{11}{14}=\frac{11}{10}$, pa je $\frac ab=\frac{11}{10}-\frac{11}{14}=\frac{77-55}{70}=\frac{22}{70}=\frac{11}{35}$.