x-y=25
xy=84
x=25+y
25y+y^2=84
y^2+25y-84=0
D=25^2-4*(-84)=961=31^2
y1=(-25+31)/2=3
y2=(-25-31)/2=-28
x1=25+3=28
x2=25-28=-3
x-y=18
x/y=2.8
x=2.8y
2.8y-y=18
1.8y=18
y=10
x=28