For me personally, the easiest way to do this is by isolating the x² term, and finding the square root of both sides. The hardest way (well actually, the longest way) would be to use the quadratic formula. It just complicates things unnecessarily.
2x-2yd=y+xd
2x-y=xd+2yd
2x-y=d(x+2y)
(2x-y)/(x+2y)=d
So the answer is <span><span>d=<span><span>2x−y</span><span>x+2y</span></span></span></span>
