[tex]\displaystyle\bf\\\frac{3+6+9+12+...+150}{5+10+15+20+...250}=?\\\\\textbf{Dam factor comun la numarator pe 3 si la numitor pe 5.}\\\\\frac{3+6+9+12+...+150}{5+10+15+20+...250}=\\\\\\=\frac{3\Big(1+2+3+4+...+50\Big)}{5\Big(1+2+3+4+...+50\Big)}=\boxed{\bf\frac{3}{5}}~~~(fractie~ireductibila)\\\\\textbf{Paranteza de la numarator eate identica cu cea de la numitor.}\\\textbf{Am simplificat fractia cu continutul parantezei.}\\\\[/tex]
