Assume x>y.
Then, xy = 30 and x-y=20
Isolating x in both equations yield:
x=30/y and x=20+y
By the transitive property, 30/y=20+y.
Multiplying both sides by y, 30=y(20+y), which expands to 30=y^2+20y
Thus, y^2+20y-30=0
By using the quadratic formula, we find that y=(-20+-sqrt(520))/2
Simplifying sqrt(520) gives us 2sqrt(130) and so y may equal (-20+2sqrt(130))/2 or (-20-2sqrt(130))/2.
Simplifying, y may equal -10+-sqrt(130), which turns out to be approximately 1.40175425099137979136049055675 or -21.401754250991379791360490255668
If we substitute each of these values in the equation x-y=20, then we find that x may be (approximately) 21.401754250997379791360490255668 or -1.40175425099379791360490255668.