(3a+2b):45=20 rest 15
3a+2b=45×20+15
3a+2b=915
a/b=35/39=>39a=35b=>a=35b/39
daca 3a+2b=915 si a=35b/39 inlocuim
3×35b/39+2b=915 (39 cu 3 se simplifica)
35b/13+2b=915 (aduc la acelasi numitor)
35b/13+2×13b/13=915
35b/13+26b/13=915
61b/13=915
b=915×13/61
b=11895/61
b=195
acum am a=35b/39 si b=195 inlocuim
a=35×195/39
a=6825/39
a=175