[tex] \frac{a}{b} = \frac{84}{126} \\ aducem \: fractia \: a \: supra \: b \: la \: o \: forma \: ireductibila \\ siplificam \: prin \: 2 \\ \frac{84}{126} = \frac{42}{63} \\ siplificam \: prin \: 3 \\ \frac{42}{63} = \frac{14}{21} \\ se \: mai \: simplifica \: prin \: 7 \\ \frac{14}{21} = \frac{2}{3} \\ a = 2 \\ b = 3 \\ a + b = 2 + 3 = 5[/tex]
