redlights: I picked this one up today. I was in the area and figured that this one had had a pretty good run. I mean 4 months shy of five years is good enough.
To solve the puzzle finders had to make each equation follow the law of conservation of mass, meaning that the number of each type of atom on both sides had to be equal. For example:
2 AlCl3 + 3 Na2SO4 --> 6 NaCl + 1 Als(SO4)3 meant that the D = 3 while B = 6.
That led to a light pole next to the "Cheeseburger in Paradise" where the cache was located, hence why it fit into the "Musically Yours" set. Final location N 38° 18.673 W 076° 32.042