Х-3у=3, х^2-у^2=77, х=3+3у, х^2=9+18у+9у^2, 9+18у+9у^2-у^2=77, 8у^2+18у-68=0, 4у^2+9у-34=0, Д=81+544=625, у1=(-9-25)/8=-4,25, у2=(-9+25)/8=2. х1=3+3•(-4,25)=3-12,75=-9,75, х2=3+3•2=3+6=9.