You can solve this without WolframAlpha. Start by adding all the equations together:
4a + 4b + 4c + 4d + 4e + 4f = 326
a + b + c + d + e + f = 81.5
If each equation is called (1), (2), (3), ..., etc, then you can subtract our "master equation" from each like so:
3a + b + c + d + e + f = 43
a + b + c + d + e + f = 81.5
Subtract, so 2a = -38.5 and a = -19.25.
The numbers may be incorrect, but you get the idea.