8/x-8/y=16/15y=8-x8/x-8/(8-x)=16/15(8/x-8/(8-x))*x=16/15*x(16x-64)/(x-8)=16x/15(16x-64)/(x-8)*(x-8)=16x/15*(x-8)-16x+64=(-16x^2)/15+128x/15(16x^2)/15-368x/15+64=0D=(-368/15)^2-4*(16/15)*64=73984/225x1=(√(73984/225)-(-368/15))/(2*(16/15))=20x2=(-√(73984/225)-(-368/15))/(2*(16/15))=3 км в часy=8-3=5 км в час